remote learning packet - great hearts irving, serving ... · 4/10/2020  · for today, we’re...

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Remote Learning Packet Please submit scans of written work in Google Classroom at the end of the week. May 4-8, 2020 Course : 10 Precalculus Teacher(s) : Mr. Simmons Weekly Plan : Monday, May 4 Story time! Problems 11-14 and 16 from “Relationship between Trig Functions” Tuesday, May 5 Read “Radian measure.” Wednesday, May 6 Problems 1-14 Thursday, May 7 Read “Introduction to the Polar Plane Friday, May 8 Attend office hours Catch up or review the week’s work Statement of Academic Honesty I affirm that the work completed from the packet is mine and that I completed it independently. _______________________________________ Student Signature I affirm that, to the best of my knowledge, my child completed this work independently _______________________________________ Parent Signature

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Page 1: Remote Learning Packet - Great Hearts Irving, Serving ... · 4/10/2020  · For today, we’re going to do a few more problems from “Relationships between Trig Functions” before

 

Remote Learning Packet Please submit scans of written work in Google Classroom at the end of the week.

May 4-8, 2020 Course: 10 Precalculus Teacher(s): Mr. Simmons Weekly Plan: Monday, May 4 ⬜ Story time! ⬜ Problems 11-14 and 16 from “Relationship between Trig Functions” Tuesday, May 5 ⬜ Read “Radian measure.” Wednesday, May 6 ⬜ Problems 1-14 Thursday, May 7 ⬜ Read “Introduction to the Polar Plane Friday, May 8 ⬜ Attend office hours ⬜ Catch up or review the week’s work Statement of Academic Honesty I affirm that the work completed from the packet is mine and that I completed it independently. _______________________________________Student Signature

I affirm that, to the best of my knowledge, my child completed this work independently _______________________________________ Parent Signature

Page 2: Remote Learning Packet - Great Hearts Irving, Serving ... · 4/10/2020  · For today, we’re going to do a few more problems from “Relationships between Trig Functions” before

Monday, May 4

1. Story time! If technologically feasible, email me with a story! Also, please email me if you have questions about trigonometry. BUT. Please make your questions specific. At least give me a page number where you got confused. Better yet, tell me exactly what words you read that confused you. For today, we’re going to do a few more problems from “Relationships between Trig Functions” before moving on to radians:

2. Complete Problems 11-14 and 16 on pp. 122-123. Tuesday, May 5

1. Read “Radian Measure” on pp. 124-133. Wednesday, May 6

1. Complete Problems 1-14 on pp. 133-135. Thursday, May 7

1. Read “Introduction to the Polar Plane” on pp. 135-143.

Page 3: Remote Learning Packet - Great Hearts Irving, Serving ... · 4/10/2020  · For today, we’re going to do a few more problems from “Relationships between Trig Functions” before

Uni

t fou

r – 1

22

2.)

Let u

s co

mpl

ete

Exam

ple

1c. I

f sin𝛼

=𝑎

, wha

t are

the

six

Trig

ratio

s?

3.)

Now

let t

an𝛼

=𝑑

. (A

) W

hat a

re th

e six

Trig

ratio

s gi

ven

this?

(B

) Co

mpa

re th

is an

swer

to th

e pr

evio

us.

4.)

In E

xam

ple

1c, w

e le

t th

e le

ngth

of t

he h

ypot

enus

e of

the

tria

ngle

to

equa

l 1. I

s th

at O

K? W

hy d

on’t

we

let

the

hypo

tenu

se e

qual

𝑐,

to a

llow

for

any

and

all

poss

ibili

ties?

Now

sup

pose

sin𝛼

=𝑥 𝑐, a

nd th

e le

ngth

s of

you

r tria

ngle

are

𝑎,𝑏

, and

𝑐,

with

the

hypo

tenu

se e

qual

ing 𝑐.

(A

) W

hat a

re th

e six

Trig

ratio

s?

(B)

Com

pare

this

with

the

prev

ious

two

resu

lts.

5.)

Giv

en th

e Tr

ig fu

nctio

ns a

nd a

ngle

mea

sure

, writ

e th

e eq

uiva

lent

cof

unct

ion.

(A

) si

n3

(B)

cos

10

° (C

) co

t7

° (D

) se

c64

° (E

) co

s3

(F)

tan

14

° (G

) cs

c4

(H)

sin2

(I)

tan( 𝛽

+𝛾)

(J)

sin𝛽

6.

) W

rite

out a

ll of

the

cofu

nctio

n id

entit

ies,

incl

udin

g th

e on

es w

e di

scov

ered

in th

e re

adin

g. H

int:

The

re a

re s

ix o

f the

m.

7.)

Now

writ

e ou

t all

of th

e re

cipr

ocal

iden

titie

s. H

int:

The

re a

re s

ix o

f the

m.

8.)

Eval

uate

the

follo

win

g.

(A)

sin

23

(B)

cos2

30

° (C

) ta

n2

30

° (D

) co

s24

(E)

tan

24

(F)

sin

26

(G)

cos2

60

° (H

) ta

n2

60

° (I)

si

n( 3

0°2)

(J)

cos2𝛼

9.

) W

rite

out a

tabl

e of

val

ues f

or s

in2𝛼

,co

s2𝛼

, and

tan

2𝛼

, sta

rtin

g at

𝛼=

0, g

oing

up

by 5

° eac

h ro

w, a

nd e

ndin

g at

𝛼=

90

°. Yo

u w

ill n

eed

a ca

lcul

ator

for t

his

Exer

cise

. 10

.) U

se y

our r

esul

ts fr

om th

e pr

evio

us E

xerc

ise to

ans

wer

the

follo

win

g qu

estio

ns.

(A)

Wha

t is

the

max

imum

val

ue o

f sin

2𝛼

,co

s2𝛼

, and

tan

2𝛼

? (B

) W

hat i

s th

e m

inim

um v

alue

of s

in2𝛼

,co

s2𝛼

, and

tan

2𝛼

? (C

) Ar

e th

ere

any

simila

ritie

s or

diff

eren

ces

betw

een

sin

2𝛼

and

sin𝛼

? Co

mpa

re

your

resu

lts fr

om th

e pr

evio

us s

ectio

n.

11.)

One

of

the

mos

t im

port

ant

rela

tions

hips

in

Trig

onom

etry

is

the

Pyth

agor

ean

Iden

tity

we

disc

usse

d in

the

read

ing.

Writ

e th

is id

entit

y do

wn

now

. 12

.) Ev

alua

te th

e fo

llow

ing.

(A

) si

n2

60

°+

cos2

60

° (B

) co

s23

+si

n2

30

° (C

) si

n2(𝛼

2)

+co

s2(𝛼

2)

(D)

sin

2( 3𝛼

+𝜋)

+co

s2( 3𝛼

+𝜋)

13.)

It is

ofte

n he

lpfu

l to

rew

rite

sin

2𝛼

or c

os2𝛼

. Use

the

Pyth

agor

ean

Iden

tity

to re

writ

e si

n2𝛼

and

co

s2𝛼

. 14

.) Si

mpl

ify th

e fo

llow

ing.

§3

Rel

atio

nshi

ps b

etw

een

the

Trig

func

tions

– 1

23

(A)

tan𝛼∙c

sc𝛼

(B

) ( s

in𝛼

+co

s𝛼)2

15

.) Ar

e th

ere

any

othe

r Pyt

hago

rean

Iden

titie

s? T

o fin

d th

is o

ut, u

se a

cal

cula

tor a

nd

try

the

follo

win

g fo

r diff

eren

t val

ues

of 𝛼

. (A

) se

c2𝛼

+cs

c2𝛼

(B

) ta

n2𝛼

+co

t2𝛼

(C

) Th

ere

are

two

othe

r Py

thag

orea

n Id

entit

ies.

Firs

t, us

ing

the

prev

ious

tw

o,

gues

s w

hat t

hey

mig

ht b

e. T

hen,

if y

ou c

an’t

figur

e it

out,

look

them

up

and

writ

e th

em d

own

now

. We’

ll di

scov

er h

ow to

arr

ive

at th

ese

resu

lts w

hen

we

have

som

e be

tter

tool

s. 16

.) An

swer

Tru

e or

Fal

se.

(A)

sin𝛼

=co

s(𝛼−

90

°)

(B)

sin

2𝛼

+co

s2𝛽

=1

iff 𝛼

+𝛽

=9

(C)

sin

2𝛼

=si

n𝛼∙𝛼

(D

) si

n2𝛼

is s

omet

imes

neg

ativ

e.vi

vi A

ssum

e 𝛼∈ℝ

.

Page 4: Remote Learning Packet - Great Hearts Irving, Serving ... · 4/10/2020  · For today, we’re going to do a few more problems from “Relationships between Trig Functions” before

Uni

t fou

r – 1

24

Uni

t fiv

e Ra

dian

s an

d th

e U

nit C

ircle

“Deg

rees

are

fin

e fo

r ev

eryd

ay m

easu

rem

ents

. Bu

t T

rigo

nom

etry

mar

ks a

tu

rnin

g p

oin

t in

mat

h, w

hen

th

e st

ud

ent

lift

s h

is g

aze

from

th

e ev

eryd

ay t

owar

ds

larg

er, m

ore

dis

tan

t id

eas.

You

beg

in e

xplo

rin

g ba

sic

rela

tion

ship

s, d

eep

sym

met

ries

, th

e ki

nd

s of

pat

tern

s th

at m

ake

the

un

iver

se t

ick.

An

d t

o n

avig

ate

that

ter

rain

, you

nee

d a

not

ion

of a

ngl

es

that

’s m

ore

nat

ura

l, m

ore

fun

dam

enta

l, th

an s

lici

ng

up

th

e ci

rcle

into

an

arb

itra

ryn

um

ber

of p

iece

s. T

he

nu

mbe

r π

, str

ange

th

ough

it m

ay s

eem

, lie

s at

th

e h

eart

of

mat

hem

atic

s. T

he

nu

mbe

r 36

0 d

oesn

’t. C

lin

gin

g to

th

at B

abyl

onia

n a

rtif

act

wil

l on

ly

dis

trac

t yo

u a

nd

obs

cure

th

e el

egan

t tr

uth

s yo

u’r

e se

arch

ing

for.

Ben

Orl

in

§1

Rad

ian

mea

sure

– 1

25

Up

to t

his

poin

t, w

e’ve

mea

sure

d al

l of

our

ang

les

usin

g de

gree

s. In

thi

s un

it, w

e’ll

ende

avor

to fi

nd a

diff

eren

t and

per

haps

bet

ter m

etho

d of

mea

surin

g an

gles

. The

n w

e’ll

use

that

to g

raph

poi

nts

in a

new

type

of p

lane

. Fin

ally

, afte

r thi

s, w

e in

trod

uce

perh

aps

the

mos

t im

port

ant t

hing

in T

rigon

omet

ry:

The

Uni

t Circ

le.

§1

Radi

an m

easu

re

Deg

rees

wer

e in

vent

ed m

illen

nia

ago,

per

haps

by

the

anci

ent

peop

les

livin

g in

mod

ern

day

Iraq.

Kno

win

g th

e or

igin

s of

thi

s un

it co

uld

shed

som

e lig

ht o

n its

use

fuln

ess,

and

whe

ther

ther

e isn

’t a

mor

e us

eful

uni

t to

use.

Ther

e ar

e va

rious

the

orie

s as

to

why

deg

rees

wer

e us

ed a

nd w

hy t

hey

are

the

way

tha

t ar

e. A

lmos

t cer

tain

ly, h

owev

er, i

t has

to d

o w

ith a

circ

le. A

s w

ith a

nyth

ing,

it’s

ofte

n us

eful

to

cons

ider

por

tions

or

fract

ions

of t

he w

hole

.i The

anc

ient

s ch

ose

to c

hop

the

circ

le u

p in

to 3

60

equ

al p

ortio

ns, c

allin

g th

e an

gle

crea

ted

by e

ach

port

ion

a de

gree

, as

(par

tially

) sh

own

in F

igur

e 47

.

Why

36

0?

Perh

aps

beca

use

it is

a n

ice

num

ber

with

man

y fa

ctor

s. So

cut

ting

a ci

rcle

in

half

give

s yo

u a

nice

num

ber o

f 18

0°,

in th

irds

12

0°,

four

ths

90

°, an

d so

on.

Thi

s m

eans

i T

his

is w

hy, f

or e

xam

ple,

we

have

yar

ds. C

ould

you

imag

ine

mea

surin

g th

ings

if th

e sm

alle

st u

nit w

e co

uld

get w

as m

iles?

And

eve

n th

at is

n’t e

noug

h, w

hich

is w

hy c

ontin

ue to

sub

divi

de th

e un

its s

mal

ler a

nd

smal

ler.

Figu

re 4

7

Each

of t

he in

divi

dual

spo

kes

abov

e m

easu

res

a sin

gle

degr

ee. I

f we

wer

e to

con

tinue

cre

atin

g th

ese

spok

es, t

here

wou

ld

be 3

60

of t

hem

.

Page 5: Remote Learning Packet - Great Hearts Irving, Serving ... · 4/10/2020  · For today, we’re going to do a few more problems from “Relationships between Trig Functions” before

Uni

t fiv

e –

126

that

com

mon

ly u

sed

ratio

s ar

e le

ft w

ith a

who

le n

umbe

r. Th

is w

ould

n’t b

e th

e ca

se if

the

num

ber,

say,

10

, was

use

d. T

hen

only

a h

alf-

circ

le a

nd a

fifth

-of-

a-ci

rcle

wou

ld h

ave

who

le

num

bers

. Ano

ther

sup

posit

ion

is th

at t

here

are

app

roxi

mat

ely

36

0 d

ays

in a

yea

r. An

d sin

ce, e

ach

year

, sea

sons

rep

eat

them

selv

es, a

circ

le m

akes

a n

ice

repr

esen

tatio

n of

a

cale

ndar

.

Wha

teve

r the

reas

on, h

owev

er, w

e w

ant t

o se

e if

ther

e is

a b

ette

r way

of m

easu

ring

angl

es.

Of

cour

se, “

bett

er”

is r

elat

ive,

and

diff

eren

t si

tuat

ions

mig

ht c

all f

or d

iffer

ent

units

. So

whe

n w

e sa

y “b

ette

r,” p

erha

ps w

hat

we

shou

ld s

ay is

mor

e ap

prop

riate

for

our

wor

k in

Tr

igon

omet

ry.

Cons

ider

the

circ

le s

how

n in

Fig

ure

48. W

hat i

s th

e le

ngth

of t

he a

rc fr

om 𝐴

to 𝐵

?

Ther

e ar

e a

few

way

s w

e co

uld

answ

er t

his

ques

tion.

One

is

to m

easu

re i

t th

e ol

d-fa

shio

ned

way

. Tha

t, ho

wev

er, l

eave

s ro

om fo

r err

or, a

nd w

ould

n’t h

elp

us to

mea

sure

an

arc

from

a d

iffer

ent c

ircle

. Ano

ther

way

we

coul

d do

it is

to fi

nd th

e ci

rcum

fere

nce

of th

e ci

rcle

, the

n m

ultip

ly b

y th

e fra

ctio

n of

the

outs

ide

of th

e ci

rcle

repr

esen

ted

by 𝐴

��.ii T

his

isn’t

the

wor

st t

hing

in t

he w

orld

, but

the

n… H

ow w

ill w

e m

easu

re t

hean

gle

whi

ch w

ill

allo

w u

s to

find

the

fract

ion

of th

e ou

tsid

e of

the

circ

le th

at 𝐴��

take

s up

? As

you

can

see

, w

e ha

ve a

bit

of a

n is

sue.

As w

e’ve

don

e a

few

tim

es in

this

cou

rse,

we

shou

ld g

o ba

ck to

wha

t we

know

for c

erta

in.

We

know

that

the

circ

umfe

renc

e of

a c

ircle

is

𝐶=2𝜋𝑟,

ii F

or e

xam

ple,

if th

e ar

c w

ere

half

of th

e ou

tsid

e of

the

circ

le, y

ou w

ould

mul

tiply

the

circ

umfe

renc

e of

the

circ

le b

y 1 2, r

ight

?

Figu

re 4

8

§1

Rad

ian

mea

sure

– 1

27

whe

re 𝑟

is th

e ra

dius

of a

circ

le a

nd 𝜋

is th

e m

athe

mat

ical

con

stan

t app

roxi

mat

ely

equa

l to

3.14

. We

also

kno

w th

at e

very

radi

us in

a c

ircle

is c

ongr

uent

. And

that

’s ab

out i

t. Bu

t th

is do

es s

how

us

that

if w

e’re

tryi

ng to

figu

re s

tuff

out a

bout

a c

ircle

, it i

s us

ually

a g

ood

idea

to in

volv

e a

radi

us. T

hat’s

wha

t we’

ll do

in F

igur

e 49

.

In k

eepi

ng w

ith o

ur tr

aditi

on, w

e’ve

use

d th

e La

tin le

tter

s 𝑟

and 𝑎

for t

he le

ngth

s of

the

radi

us a

nd a

rc re

spec

tivel

y.

Now

, let

’s se

e w

hat h

appe

ns w

hen

we

rela

te th

e ra

dius

to th

e ar

c le

ngth

. Let

’s as

sum

e fo

r a

mom

ent t

hat 𝑟

=𝑎

, i.e

., th

at th

e ra

dius

is th

e sa

me

leng

th a

s 𝐴��

. Thi

s w

ould

allo

w u

s to

cr

eate

that

ang

le s

een

in F

igur

e 50

, rig

ht?

This

angl

e, w

hich

we’

ll ca

ll 𝛼

, is

uniq

ue. I

n ot

her w

ords

, the

re is

one

and

onl

y on

e an

gle

for w

hich

the

radi

us is

the

sam

e le

ngth

as 𝐴��

. Fig

ure

51 s

how

s th

is to

be

true

.

Figu

re 4

9

Figu

re 5

0

Page 6: Remote Learning Packet - Great Hearts Irving, Serving ... · 4/10/2020  · For today, we’re going to do a few more problems from “Relationships between Trig Functions” before

Uni

t fiv

e –

128

This

is in

tere

stin

g fo

r a c

oupl

e of

reas

ons.

Firs

t of a

ll, n

otic

e th

at th

ere

is on

e an

d on

ly o

ne

angl

e th

at c

omes

out

as

a co

nseq

uenc

e of

the

com

paris

on t

o th

e ra

dius

and

arc

leng

th.

Seco

ndly

, and

per

haps

mor

e im

port

antly

, the

siz

e of

the

circ

le (

and,

by

exte

nsio

n), t

he

leng

ths

of th

e ra

dius

and

arc

, won

’t m

atte

r.iii T

hus

we

mak

e th

e fo

llow

ing

defin

ition

.

Radi

an m

easu

re

The

angl

e fo

rmed

by

the

ratio

of t

he a

rc le

ngth

𝑎 to

the

radi

us 𝑟

in a

circ

le. S

ymbo

lical

ly,

𝛼𝑟𝑎𝑑

=𝑎 𝑟

,

whe

re 𝑟

is th

e ra

dius

and

𝑎 is

the

leng

th o

f the

arc

.

Ex

ampl

e 1a

Wha

t doe

s an

ang

le m

easu

re o

f 1 ra

dian

look

like

?

This

is a

n ex

celle

nt q

uest

ion,

and

a g

reat

star

ting

poin

t to

see

the

intu

ition

beh

ind

radi

ans.

A ra

dian

is a

ratio

bet

wee

n th

e ar

c le

ngth

and

the

radi

us, o

r 𝑎 𝑟

, whe

re 𝑟

is th

e ra

dius

of a

iii W

e’ll

show

this

expl

icitl

y in

the

fort

hcom

ing

Exam

ples

.

Figu

re 5

1

Her

e,𝑏

=1

.5𝑟.

As

a co

nseq

uenc

e of

this

incr

ease

d ar

c siz

e, th

e an

gle

is la

rger

, and

ther

efor

e 𝛼≠𝛽

.

§1

Rad

ian

mea

sure

– 1

29

circ

le a

nd 𝑎

is th

e le

ngth

of t

he a

rc w

e’re

con

cern

ed w

ith. U

sing

our d

efin

ition

, the

n, w

e ha

ve

1=𝑎 𝑟

.

But t

his

will

onl

y be

true

if 𝑎

=𝑟.

The

refo

re, a

mea

sure

of 1

radi

an w

ill lo

ok li

ke F

igur

e 52

, w

here

the

radi

us a

nd 𝐴��

are

equ

al.

Not

ice

that

our

ang

le m

easu

re is

1?

You

mig

ht b

e w

onde

ring

wha

t the

uni

ts o

f thi

s an

gle

mea

sure

are

, but

the

re a

ren’

t an

y! Y

ou c

ould

say

1 r

adia

n, b

ut if

an

angl

e m

easu

re is

re

port

ed w

ith n

o un

it, it

is a

ssum

ed to

be

mea

sure

d in

radi

ans.

iv

Did

you

not

ice

that

our

circ

le h

ad a

radi

us a

nd a

rc le

ngth

of 3

? W

e w

ante

d an

ang

le o

f 1,

and

that

is o

nly

true

whe

n 𝑟

=𝑎

. So

we

coul

d ha

ve a

lso

chos

en 𝑟

=𝑎

=5

, or 𝑟

=𝑎

=1

00

, (a

nd s

oon

) if w

e w

ante

d to

. Do

you

see

why

?

Exam

ple

1b

Wha

t doe

s an

ang

le o

f 2 lo

ok li

ke?

This

is a

sim

ilar q

uest

ion,

so

we

agai

n go

bac

k to

the

defin

ition

. The

equ

atio

n

2=𝑎 𝑟

mus

t be

tru

e. T

here

is a

n in

finite

am

ount

of

poss

ibili

ties

for

both

𝑎 a

nd 𝑟

, suc

h as

𝑎=

6,𝑟

=3

(whi

ch w

e sh

ow in

Fig

ure

53).

iv T

his

is a

noth

er re

ason

to p

refe

r rad

ians

.

Figu

re 5

2

We’

ve c

hose

n a

radi

us a

nd a

rc le

ngth

of 3

, but

we

coul

d ha

ve e

asily

cho

sen

any

othe

r len

gth

so lo

ng a

s 𝑟

=𝑎

.

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Uni

t fiv

e –

130

The

prev

ious

tw

o ex

ampl

es w

ere

ther

e to

hel

p yo

u ge

t a

gras

p on

rad

ians

, but

we

still

ha

ven’

t see

n its

bes

t fea

ture

. We

expl

ore

that

now

.

Exam

ple

2a

Wha

t is

the

leng

th o

f the

radi

us g

iven

Fig

ure

54?

Now

this

is in

tere

stin

g. W

e ar

e gi

ven

an a

ngle

and

an

arc

leng

th, a

nd a

re to

ld to

find

the

leng

th o

f the

rad

ius.

Usi

ng t

he d

efin

ition

of a

rad

ian,

we

can

wor

k ba

ckw

ard

and

easil

y ge

t the

ans

wer

. Sin

ce, a

ccor

ding

to o

ur d

efin

ition

, we

have

3=24 𝑟

,

we

sim

ply

solv

e th

e pr

evio

us e

quat

ion

for 𝑟

and

get

𝑟=

8.

Easy

! But

to

real

ly a

ppre

ciat

e ra

dian

s, co

nsid

er F

igur

e 55

, whe

re w

e ha

ve u

sed

degr

ees

inst

ead.

Figu

re 5

3

As y

ou c

an s

ee, t

he ra

tio is

wha

t’s im

port

ant.

The

fact

that

the

arc

leng

th is

twic

e th

e le

ngth

of t

he ra

dius

is w

hat t

ells

us

we

have

an

angl

e m

easu

re o

f 2. A

ppre

ciat

e, a

lso, h

ow th

e an

gle

is cl

early

diff

eren

t fro

m th

e pr

evio

us E

xam

ple.

Figu

re 5

4

§1

Rad

ian

mea

sure

– 1

31

Coul

d w

e fin

d 𝑟?

The

ans

wer

is

no –

deg

rees

are

a m

easu

rem

ent

foun

d co

mpl

etel

y in

depe

nden

t of t

he s

ize

of a

circ

le. T

hus

it of

fers

us

no h

elp

at a

ll. R

adia

ns, t

here

fore

, giv

e us

free

info

rmat

ion!

Exam

ple

2b

Wha

t is

the

leng

th o

f the

arc

sub

tend

edv b

y an

ang

le o

f 6 a

nd a

radi

us o

f 10

?

No

pict

ure

is pr

ovid

ed, a

nd it

wou

ld b

e he

lpfu

l for

you

dra

w o

ne, b

ut it

is n

ot n

eces

sary

. W

e sim

ply

use

the

defin

ition

:

6=

𝑎 10

.

Hen

ce

𝑎=

60

.

Ther

e ar

e a

few

mor

e im

port

ant q

uest

ions

whi

ch m

ust b

e as

ked

if w

e ar

e to

suc

ceed

with

ra

dian

s. Fo

r exa

mpl

e, h

ow m

any

radi

ans

are

in a

full

rota

tion?

We

know

ther

e ar

e 3

60

° in

a fu

ll ro

tatio

n, b

ut w

hat a

bout

radi

ans?

Let u

s ans

wer

this

que

stio

n w

ith a

spec

ific

circ

le, a

nd th

en g

ener

aliz

e af

terw

ards

. Con

sider

a

circ

le w

ith a

radi

us o

f 1.vi

Sinc

e th

e de

finiti

on o

f a ra

dian

tells

us

that

𝛼𝑟𝑎𝑑

=𝑎 𝑟

,

And

we

have

𝑟=

1, w

e ha

ve

v T

his

is a

fanc

y, p

erha

ps o

ld-f

ashi

oned

wor

d w

hich

mea

ns fo

rmed

or c

reat

ed b

y. S

o th

e ar

c is

cre

ated

by

the

angl

e.

vi W

e co

uld

have

cho

sen

any

valu

e fo

r the

radi

us, b

ut w

e ch

ose

1. A

ny th

ough

ts o

n w

hy w

e w

ould

cho

ose

this

num

ber a

nd n

ot, s

ay, 2

3?

Figu

re 5

5

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Uni

t fiv

e –

132

𝛼𝑟𝑎𝑑

=𝑎

.

If w

e ar

e co

nsid

erin

g a

full

rota

tion,

how

ever

, we

are

not

look

ing

at a

n ar

c, b

ut t

he fu

ll ci

rcum

fere

nce

of th

e ci

rcle

. The

refo

re, 𝑎

=2𝜋

and

hen

ce

𝛼𝑟𝑎𝑑

=2𝜋

.

This

is a

n im

port

ant f

act,

and

we

list i

t bel

ow fo

r you

r con

veni

ence

.

Radi

ans

in v

ario

us ro

tatio

ns

Full

rota

tion:

2𝜋

Hal

f rot

atio

n: 𝜋

Q

uart

er ro

tatio

n: 𝜋 2

Th

us, t

here

are

2𝜋

radi

ans

in a

full

rota

tion.

This

allo

ws

us t

o an

swer

our

nex

t m

ost

impo

rtan

t qu

estio

n:

How

do

radi

ans

rela

te t

o de

gree

s? In

oth

er w

ords

, how

doe

s on

e co

nver

t fro

m o

ne to

the

othe

r?

To fi

nd t

his

answ

er, l

et u

s fin

d ou

t ho

w m

any

degr

ees

are

in o

ne r

adia

n. T

o do

thi

s, w

e ju

st n

eed

to c

onve

rt. W

e w

ill u

se d

imen

sion

al a

naly

sis

to h

elp

us d

o th

is, a

s w

e sh

ow

belo

w.

36

1 r

ota

tio

n

=

18

57

.30

° 1

ro

tati

on

2𝜋

rad

ian

s 𝜋

rad

ian

s 1

rad

ian

Th

e ro

tatio

ns c

ance

l, an

d le

ave

us w

ith o

ur re

sult

of a

ppro

xim

atel

y 5

7.3

° for

eve

ry 1

radi

an.

This

is a

str

ange

num

ber,

and

we

will

rar

ely

use

it. In

stea

d, t

he f

ract

ion

180

𝜋 is

wha

t yo

u

shou

ld m

emor

ize

and

beco

me

com

fort

able

with

. Tha

t sai

d,it

is he

lpfu

l to

know

how

muc

h 1

radi

an is

in d

egre

es, s

ince

it w

ill h

elp

you

get a

pic

ture

of w

hat y

ou’re

wor

king

with

.

Exam

ple

3a

Conv

ert 6

radi

ans

into

deg

rees

.

Sinc

e th

ere

are 180

𝜋 d

egre

es f

or e

very

one

rad

ian,

we

sim

ply

mul

tiply

thi

s nu

mbe

r by

6.

Thus

6 ra

dian

s is

34

3.8

°.

Exam

ple

3b

Conv

ert 7

5° i

nto

radi

ans.

This

is th

e op

posit

e of

the

prev

ious

pro

blem

. Thu

s, w

e ne

ed a

new

con

vers

ion

fact

or. W

e ap

ply

the

sam

e pr

inci

ple

to o

btai

n a

conv

ersio

n fa

ctor

:

§1

Rad

ian

mea

sure

– 1

33

2𝜋

1

ro

tati

on

=

𝜋

1

ro

tati

on

3

60

° 1

80

Th

is te

lls u

s th

at o

ne d

egre

e is

𝜋

180 r

adia

ns. A

nd s

ince

we

wan

t to

fin

d ou

t ho

w m

any

radi

ans

75

° is,

we

just

mul

tiply

the

prev

ious

by

𝜋

180. W

e ge

t

75∙𝜋

18

0=

75𝜋

18

0=

5𝜋

12

.

Whe

n w

orki

ng w

ith ra

dian

s, w

e ne

ver w

ant a

n ap

prox

imat

ion.

Did

you

not

ice

how

sim

ilar

the

conv

ersi

on f

acto

rs w

ere?

You

sho

uld

have

the

m

mem

oriz

ed, a

s yo

u’ll

need

them

in th

is s

ectio

n an

d be

yond

.

§𝟏 E

xerc

ises

1.)

Det

erm

ine

the

mea

sure

of 𝛼

(in

radi

ans)

giv

en th

e fo

llow

ing

radi

i and

arc

leng

ths.

(A)

𝑟=

10

,𝛼=2

0

(B)

𝑟=

30

,𝛼=

10

(C

) 𝑟

=1

5,𝛼

=1

00

(D

) 𝑟

=3 4

,𝛼=

16

2.

) D

eter

min

e th

e le

ngth

of 𝐴��

giv

en t

he f

ollo

win

g ra

dii a

nd a

ngle

s. Th

en s

ketc

h a

circ

le w

ith th

e gi

ven

info

rmat

ion

and

the

leng

th o

f the

arc

. (A

) 𝑟

=5

,𝛼=2

(B

) 𝑟

=3

,𝛼=

3

(C)

𝑟=

5 3,𝛼

=3 4

(D) 𝑟

=1

0,𝛼

=1 2

3.)

Det

erm

ine

the

leng

th o

f the

radi

us g

iven

the

follo

win

g ar

c le

ngth

s an

d an

gles

. (A

) 𝐴��

=3

5,𝛼

=7

(B

) 𝐴��

=5

,𝛼=

5

(C)

𝐴��

=1

0,𝛼

=3

(D

) 𝐴��

=6

,𝛼=

1 2

4.)

Sket

ch th

e fo

llow

ing

angl

es.

(A)

1

(B) 2

(C

) 3

(D

) 4

(E)

5

(F)

6

(G)

0.5

(H

) 6

.28

5.

) Co

nver

t the

follo

win

g an

gle

mea

sure

from

ang

les

to ra

dian

s or

vic

e ve

rsa.

(A

) 2

00

° (B

) 1

00

° (C

) 5

(D)

1.5

(E)

𝜋 12

(F)

72

(G)

𝜋 5

(H) 𝜋

6.

) Th

e fo

llow

ing

Figu

re is

a c

ircle

with

var

ious

rota

tions

on

it. A

ssum

e th

at 𝐶

is lo

cate

d at

the

orig

in,

and

that

the

re a

re f

our

Qua

dran

ts,

as n

orm

ally

def

ined

on

a co

ordi

nate

pla

ne. E

ach

angl

e be

gins

with

𝐴𝐶

, the

n ro

tate

s co

unte

r-cl

ockw

ise u

p to

the

next

poi

nt.

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Uni

t fiv

e –

134

(A)

Writ

e ea

ch o

f the

ang

le m

easu

res

in ra

dian

s.vi

i (B

) W

hich

is th

e la

rger

ang

le, 𝜋 4

or 𝜋 2

? (C

) As

sum

e th

at w

e co

ntin

ue th

is pa

tter

n, s

o th

at in

Qua

dran

t II t

he n

ext a

ngle

is

30

° m

ore

than

90

°, th

en 4

mor

e th

an 9

0°,

and

so o

n (in

clud

ing

Qua

dran

ts II

I and

IV).

Writ

e ea

ch o

f the

se a

ngle

s in

deg

rees

. (D

) N

ow w

rite

each

of t

he a

ngle

s yo

u fo

und

in (C

) in

radi

ans.

7.)

One

of t

he p

robl

ems

that

stu

dent

s ha

ve w

ith r

adia

ns is

tha

t th

ey’re

ter

rible

with

fra

ctio

ns. A

ccor

ding

ly, l

et u

s pr

actic

e ou

r fra

ctio

n in

tuiti

on.

(A)

Whi

ch n

umbe

r is

larg

er, 1 4

or 1 2?

How

can

you

tel

l with

out

havi

ng t

o di

vide

th

e nu

mer

ator

and

den

omin

ator

? (B

) M

ake

an a

rgum

ent f

or w

hy 1 4

is le

ss th

at 1 2

. (H

int:

Try

usin

g m

oney

!) (C

) Li

kew

ise,

whi

ch is

larg

er:

𝜋 3 o

r 𝜋 6?

(D)

Whe

n co

mpa

ring

a w

hole

num

ber t

o a

fract

ion,

it’s

ofte

n us

eful

to c

onve

rt

the

who

le n

umbe

r in

to a

frac

tion.

For

exa

mpl

e, w

hich

is la

rger

, 2 o

r 5 3?

To

see,

let’s

con

vert

2 in

to a

frac

tion

that

has

the

sam

e de

nom

inat

or a

s 5 3. N

ow

answ

er th

e qu

estio

n: W

hich

is la

rger

, 2 o

r 5 3?

(E)

Whi

ch is

larg

er: 𝜋

or 5

𝜋 6?

(F)

Whi

ch is

larg

er: 15𝜋

4 o

r 2𝜋

?

8.)

How

can

you

tel

l tha

t 5𝜋 6 is

less

tha

n a

half-

rota

tion?

(H

int:

Try

usin

g co

mm

on

deno

min

ator

s in

you

r fra

ctio

ns.)

9.)

Whi

ch Q

uadr

ant i

s 11𝜋

6 in

? H

ow c

an y

ou q

uick

ly te

ll? (H

int:

Use

the

Figu

re fr

om 2

.) to

hel

p yo

u vi

sual

ize.

) 10

.) O

f cou

rse,

you

can

alw

ays

conv

ert t

he ra

dian

s in

to d

egre

es to

che

ck w

hich

one

is

larg

er. C

onve

rt 7𝜋 4 a

nd 5𝜋 3 in

to d

egre

es a

nd th

en d

eter

min

e w

hich

one

is la

rger

.

11.)

Now

take

7𝜋 4 a

nd 5𝜋 3 a

nd g

et c

omm

on d

enom

inat

ors.

Whi

ch o

ne is

larg

er?

vi

i And

just

to re

itera

te:

Your

ans

wer

s m

ust b

e in

exa

ct fo

rm.

§1

Rad

ian

mea

sure

– 1

35

12.)

A w

heel

has

a ra

dius

of 12

inch

es.vi

ii (A

) If

the

whe

el m

akes

a fu

ll ro

tatio

n, h

ow fa

r ha

s th

e w

heel

tra

vele

d fro

m it

s st

artin

g po

int?

(B

) If

the

whe

el m

akes

a h

alf r

otat

ion,

how

far h

as th

e w

heel

trav

eled

from

its

star

ting

poin

t?

(C)

Supp

ose

the

whe

el h

as ro

tate

d 1

0𝜋

. How

far h

as it

trav

eled

? (D

) If

the

whe

el h

as tr

avel

ed 3

6 in

ches

, how

muc

h ha

s it

rota

ted?

13

.) Su

ppos

e a

whe

el is

24

inch

es a

roun

d.

(A)

If th

e w

heel

has

rota

ted 5𝜋 6

, how

far h

as it

trav

eled

? (B

) If

the

whe

el h

as tr

avel

ed 1

0 fe

et, h

ow m

uch

has

it ro

tate

d?

14.)

Supp

ose

a w

heel

has

trav

eled

10

feet

. (A

) If

it ha

s ro

tate

d 13𝜋

6, w

hat i

s its

radi

us?

(B)

If it

has

rota

ted 3𝜋 4

, w

hat i

s its

circ

umfe

renc

e?

§2

Intr

oduc

tion

to th

e Po

lar P

lane

Afte

r a b

rief h

iatu

s, w

e no

w re

turn

to o

ur T

rig fu

nctio

ns. W

e w

ill u

se w

hat y

ou le

arne

d in

U

nit f

our e

xten

sivel

y in

this

sect

ion;

you

will

nee

d to

be

able

to c

alcu

late

Trig

ratio

s ve

ry

quic

kly.

i We

will

also

beg

in to

wor

k w

ith T

rig fu

nctio

ns w

here

our

ang

les

are

in ra

dian

s.

To h

elp

us p

ract

ice

and

mem

oriz

e th

ese

Trig

func

tions

, we

will

now

intr

oduc

e a

new

way

to

grap

h.

Befo

re w

e do

thi

s, a

few

wor

ds o

n w

hat

mak

es t

he c

oord

inat

e pl

ane

so e

ffect

ive.

The

re

are

num

erou

s w

ays

one

coul

d se

t up

a gr

aphi

ng s

yste

m, b

ut, i

deal

ly, w

e w

ould

like

it b

e sim

ple

to u

se a

nd e

ffect

ive.

The

coo

rdin

ate

plan

e is

grea

t be

caus

e it

requ

ires

just

tw

o co

mpo

nent

s (a

n 𝑥

- an

d 𝑦

-val

ue) t

o pl

ot a

ny p

oint

. So

it’s

effe

ctiv

e an

d ea

sy to

use

.

So if

we’

re g

oing

to

com

e up

with

a n

ew w

ay t

o pl

ot p

oint

s, it

shou

ld b

e ju

st a

s sim

ple

and

effe

ctiv

e. In

oth

er w

ords

, we

shou

ld c

ome

up w

ith a

sys

tem

tha

t on

ly r

equi

res

two

com

pone

nts

to p

lot

any

poin

t. An

ythi

ng m

ore

than

tha

t w

ill r

ende

r ou

r sy

stem

far

less

ef

fect

ive.

So le

t us

cons

ider

a s

yste

m th

at u

ses

circ

les

inst

ead

of re

ctan

gula

r grid

lines

, as

show

n in

Fi

gure

56.

vi

ii Ass

ume

that

the

whe

el is

a p

erfe

ct c

ircle

. i O

r, as

we

sugg

este

d, y

ou s

houl

d si

mpl

y m

emor

ize

them

.

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Uni

t fiv

e –

136

Let u

s em

phas

ize

that

we

have

circ

les

here

, not

rect

angu

lar g

ridlin

es. S

o us

ing

an 𝑥

- an

d 𝑦

-val

ue w

ill n

ot s

uffic

e. W

e ne

ed t

wo

diffe

rent

com

pone

nts

entir

ely.

How

abo

ut w

e us

e an

ang

lem

easu

re a

nd a

radi

us?

That

shou

ld a

llow

us t

o pl

ot a

ny p

oint

on

this

plan

e us

ing

only

two

com

pone

nts.

Cons

ider

Fig

ure

57. W

e ha

ve tw

o co

mpo

nent

s, 2

and

30

°. Le

t’s s

tart

with

the 2

. For

mal

ly,

it’s a

radi

us –

that

is, i

t is t

he d

istan

ce fr

om th

e ce

nter

to th

e po

int.

Anot

her w

ay o

f loo

king

Figu

re 5

6

Figu

re 5

7

§2

Intr

oduc

tion

to th

e Po

lar P

lane

– 1

37

at it

is th

at o

ur p

oint

mus

t be

on th

e se

cond

circ

le.ii T

he s

econ

d co

mpo

nent

, 30

°, te

lls u

s w

here

upo

n th

at s

econ

d ci

rcle

we

mus

t put

our

poi

nt. S

o w

e pl

ace

our p

oint

2 a

way

from

th

e or

igin

,iii th

en ro

tate

the

poin

t 30

° up.

We

show

this

proc

ess

in F

igur

es 5

8 a

and

b.

This

proc

ess

wor

ks v

ery

wel

l, so

let u

s no

w d

efin

e ou

r new

way

of g

raph

ing

Gra

phin

g on

the

Pola

r Pla

ne

A po

int 𝐴( 𝑟

,𝛼)

is pl

otte

d by

cre

atin

g a

line

segm

ent o

f len

gth 𝑟,

and

then

rota

ting

that

se

gmen

t 𝛼.

Just

like

with

the

coor

dina

te p

lane

, we

shou

ld la

bel o

ur c

ircle

s. Yo

u m

ay h

ave

notic

ed

lines

ext

rudi

ng fr

om th

e po

le, o

r orig

in o

f the

Pol

ar P

lane

. The

se li

nes

form

ang

les

with

po

sitiv

e 𝑥

-axi

s, an

d lo

ok a

wfu

lly s

imila

r to

a pr

oble

m fr

om th

e pr

evio

us s

ectio

n. W

e’ll

labe

l the

m b

elow

in F

igur

e 59

.

ii T

here

’s a

disa

dvan

tage

to th

is pe

rspe

ctiv

e, s

ince

we

coul

d al

so h

ave

1.5

as

the

radi

us. I

n th

is c

ase,

we

need

to d

raw

a c

ircle

hal

fway

bet

wee

n th

e fir

st a

nd s

econ

d ci

rcle

. So

it’s

not t

oo m

uch

of a

str

etch

to u

s th

is lo

gic.

iii W

hich

we’

ll gi

ve a

diff

eren

t nam

e sh

ortly

.

Figu

re 5

8a a

nd b

We

star

ted

by m

akin

g a

segm

ent o

f len

gth 2

, the

n ro

tatin

g th

at s

egm

ent u

p 3

0°.

Not

e th

at th

e se

gmen

t onl

y he

lps

to

plac

e th

e po

int;

wha

t we

real

ly c

are

abou

t is

the

poin

t.

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Uni

t fiv

e –

138

As w

ith th

e co

ordi

nate

pla

ne, w

e do

n’t have

to c

hoos

e th

ese

angl

es. H

owev

er, t

here

is

good

reas

on to

cho

ose

thes

e pa

rtic

ular

ang

les,

and

we’

ll re

veal

that

ans

wer

sho

rtly

.iv

Also

of i

mpo

rtan

t not

e: T

he a

ngle

mea

sure

s al

way

s st

art o

n w

hat w

e no

rmal

ly c

all t

he

posit

ive 𝑥

-axi

s an

d ro

tate

up

from

ther

e.v

Exam

ple

1a

Plot

the

poin

t 𝐴( 2

,45

°).

To d

o th

is, w

e sim

ply

go t

o ou

r se

cond

circ

le, t

hen

rota

te u

p 4

5°.

We

show

the

plo

tted

po

int i

n Fi

gure

60.

iv If

you

’ve

not a

lread

y fig

ured

it o

ut y

ours

elf.

v Thi

s is

by

conv

entio

n. S

omeo

ne s

omew

here

dec

ided

that

they

wer

e go

ing

to d

o it

that

way

, and

we’

ve a

ll fo

llow

ed s

uit.

Figu

re 5

9

§2

Intr

oduc

tion

to th

e Po

lar P

lane

– 1

39

Exam

ple

1b

Gra

ph th

e po

int 𝐵

( 3.5

,10

°).

Nei

ther

of t

he t

wo

com

pone

nts

in 𝐵

is o

n a

line,

but

, lik

e th

e co

ordi

nate

pla

ne, w

e ca

n ea

sily

appr

oxim

ate

thei

r loc

atio

ns. W

e sh

ow th

is in

Fig

ure

61.

Figu

re 6

0

Figu

re 6

1

It m

ight

be

help

ful t

o dr

aw a

line

for a

10

° ang

le. I

t mig

ht a

lso b

e he

lpfu

l to

draw

a c

ircle

hal

fway

bet

wee

n th

e th

ird a

nd

four

th c

ircle

.

Page 12: Remote Learning Packet - Great Hearts Irving, Serving ... · 4/10/2020  · For today, we’re going to do a few more problems from “Relationships between Trig Functions” before

Uni

t fiv

e –

140

Exam

ple

1c

Gra

ph th

e po

int 𝐶

(2.2

,𝜋 2).

In th

is ex

ampl

e, w

e ar

e us

ing

radi

ans

to m

easu

re o

ur a

ngle

s an

d no

t deg

rees

. Rec

allin

g th

at 9

0° a

nd 𝜋 2

are

equ

ival

ent,

we

can

easi

ly g

raph

Fig

ure

62.

Man

y of

you

r Exe

rcise

s w

ill u

se ra

dian

s, so

the

abov

e gr

aph

we’

ve p

rovi

ded

may

not

be

the

mos

t he

lpfu

l. Yo

u w

ill w

ant

to c

reat

e a

Pola

r Pl

ane

with

the

rad

ians

list

ed a

nd n

ot

degr

ees.

But d

on’t

wor

ry, t

his

will

be

one

of y

our E

xerc

ises.

We

have

not

yet

dis

cuss

ed n

egat

ive

angl

es. U

p to

this

poin

t, yo

u m

ight

thin

k th

at a

ngle

s, lik

e le

ngth

s, ca

n on

ly b

e po

sitiv

e. B

ut a

ngle

s (un

like

leng

ths)

hav

e a

dire

ctio

n. S

o fa

r we’

ve

alw

ays

rota

ted

“up”

, whi

ch h

as a

mou

nted

to

a co

unte

r-cl

ockw

ise r

otat

ion.

Not

hing

is

stop

ping

us

from

rota

ting

in th

e op

posit

e di

rect

ion,

i.e.

, clo

ckw

ise,

but

we

have

n’t h

ad a

go

od w

ay t

o la

bel t

his

othe

r th

an s

pelli

ng it

out

ent

irely

. Let

us

ther

efor

e ag

ree

that

a

nega

tive

angl

e m

easu

re te

lls u

s to

rota

te c

lock

wise

, whi

le a

pos

itive

ang

le m

easu

re te

lls

us to

rota

te c

ount

er-c

lock

wise

.

Exam

ple

2

Gra

ph th

e po

int 𝐷

( 3,−

60

°).

Figu

re 6

2

§2

Intr

oduc

tion

to th

e Po

lar P

lane

– 1

41

The

nega

tive

angl

e te

lls u

s to

rota

te 6

cloc

kwis

e. S

ince

we

know

our

poi

nt m

ust b

e on

th

e th

ird c

ircle

(du

e to

the

rad

ius

bein

g 3

), w

e ju

st n

eed

to d

eter

min

e ho

w t

o ro

tate

cl

ockw

ise. U

sing

the

sam

e Po

lar

Plan

e as

bef

ore,

but

cou

ntin

g in

the

oppo

site

dire

ctio

n (a

nd a

pply

ing

appr

opria

te la

bels)

, we

com

e up

with

Fig

ure

63.

But t

here

’s so

met

hing

qui

te c

urio

us a

s to

the

abov

e: T

his

is a

poi

nt w

e co

uld

have

mad

e us

ing

our P

olar

Pla

ne fr

om b

efor

e. If

we

take

the

sam

e po

int b

ut s

witc

h th

e la

bels

bac

k,

we

get F

igur

e 64

.

Figu

re 6

3

Perh

aps

you

notic

ed th

at w

e di

d no

t com

plet

e la

belin

g th

is Po

lar P

lane

. As

you

mig

ht h

ave

gues

sed,

yes

, thi

s w

ill b

e on

e of

yo

ur E

xerc

ises.

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Uni

t fiv

e –

142

Not

ice

that

our

poi

nt is

now

loca

ted

at (

3,3

00

°). S

o it

appe

ars a

s tho

ugh

30

0° i

s equ

ival

ent

to −

60

°. Th

is is

inte

rest

ing!

Cote

rmin

al a

ngle

s Tw

o di

ffere

nt a

ngle

s th

at e

nd u

p in

the

sam

e sp

ot a

re s

aid

to b

e co

term

inal

. So

−6

0° a

nd 3

00

° are

cot

erm

inal

, sin

ce th

ey e

nd u

p in

the

exac

t sam

e sp

ot. A

noth

er w

ay

of lo

okin

g at

thi

s is

tha

t th

e po

int

crea

ted

by (𝑟,−

60

°) a

nd (𝑟,

30

0°)

will

be

the

sam

e (w

here

𝑟∈ℝ

>0

).

Exam

ple

3

Plot

the

poin

t 𝐸( 2

,84

0°)

.

This

prob

lem

con

tain

s an

othe

r str

ange

ang

le.A

fter a

ll, th

ere

are

only

36

in a

rota

tion.

Bu

t who

’s to

say

that

we

can

only

do

one

rota

tion?

To

acco

unt f

or m

ultip

le ro

tatio

ns, w

e ca

n ha

ve a

ngle

s th

at e

xcee

d 3

60

°.vi H

ow m

any

rota

tions

is 84

0°?

Wel

l, if

36

is on

e ro

tatio

n, th

en tw

o ro

tatio

ns w

ould

be

vi L

ikew

ise,

we

can

also

hav

e an

gles

that

are

less

than

−3

60

°.

Figu

re 6

4

We’

ve le

ft th

e la

bel f

rom

the

prev

ious

Fig

ure

for y

ou to

hel

p yo

u co

mpa

re.

§2

Intr

oduc

tion

to th

e Po

lar P

lane

– 1

43

36

+3

60

°=

72

0°,

right

? Li

kew

ise, w

e ca

n se

e th

at t

hree

rot

atio

ns w

ould

be

1,0

80

°. So

it s

eem

s as

tho

ugh

we

have

two

full

rota

tions

and

then

som

e le

ft ov

er. T

o ac

coun

t for

this,

we’

ll ju

st s

ubtr

act

two

full

rota

tions

from

wha

t we

have

, 84

0°:

84

0°−

72

12

0°.

So w

e ha

ve t

wo

full

rota

tions

and

the

n 12

mor

e. T

his

help

s tr

emen

dous

ly w

hen

we

grap

h 84

0°,

since

now

all

we

have

to d

o is

iden

tify

the

12

0° a

ngle

on

our P

olar

Pla

ne. W

e sh

ow th

is in

Fig

ure

65.

This

also

tells

us

that

84

0° a

nd 12

0° a

re c

oter

min

al.

And

this,

in tu

rn, t

ells

us h

ow m

any

cote

rmin

al a

ngle

s ea

ch a

ngle

has

. Can

you

figu

re it

ou

t?

We’

ll fu

rthe

r exp

lore

thes

e id

eas

in th

e Ex

erci

ses,

as w

ell a

s pr

epar

e fo

r our

mor

e fo

rmal

in

trod

uctio

n to

the

Pola

r Pla

ne in

Uni

t sev

en. T

he b

revi

ty o

f thi

s se

ctio

n w

ill g

ive

you

time

topr

actic

e th

e ba

sics

and,

per

haps

mor

e im

port

antly

, pav

e th

e w

ay fo

r suc

cess

in th

e la

st

sect

ion

of th

is U

nit,

whi

ch is

per

haps

the

mos

t im

port

ant.

Figu

re 6

5