s3 3 trigonometry uses
DESCRIPTION
APPLICATION OF TRIANGLE.TRANSCRIPT
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TrigonometryS3
Credit
The Tangent Ratio
The Tangent using Angle
The Sine of an Angle
The Sine Ration In Action
The Cosine of an Angle
Mixed Problems
The Tangent Ratio in Action
The Tangent (The Adjacent side)
The Tangent (Finding Angle)
The Sine ( Finding the Hypotenuse)
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Starter Questionsw
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1. An F1 car can complete a lap in 2 mins.
A lap is 5 miles in length.
Show that the average speed is 150mph
2. The resistance (R) in copper wire is directly
proportion to its length (L) and inversely to
the square of its radius (r).
Write down an formula connecting R, L and r.
S3 Credit
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7-Sep-14 Created by Mr. Lafferty Maths Dept.
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Learning Intention Success Criteria
2. Work out Tan Ratio.
1. To identify the hypotenuse, opposite and adjacent sides in a right angled triangle.
Angles & Triangles
1. Understand the terms hypotenuse, opposite and adjacent in right angled triangle.
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Let’s Investigate!
TrigonometryS3
Credit
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TrigonometryS3
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Trigonometry means “triangle” and “measurement”.
AdjacentOpposite
x°
We will be using right-angled triangles.
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TrigonometryS3
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30°
Adjacent
Opposite
OppositeAdjacent
= 0.6
Mathemagic!
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TrigonometryS3
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45°
Adjacent
Opp
osite
OppositeAdjacent
= 1
Try another!
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TrigonometryS3
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For an angle of 30°, OppositeAdjacent
= 0.6
We write tan 30° = 0.6
Opposite
Adjacentis called the tangent of an angle.
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Trigonometry
Tan 25° 0.466
Tan 26° 0.488
Tan 27° 0.510
Tan 28° 0.532
Tan 29° 0.554
Tan 30° 0.577
Tan 31° 0.601
Tan 32° 0.625
Tan 33° 0.649
Tan 34° 0.675
Tan 30° = 0.577
Accurate to 3 decimal places!
The ancient Greeks discovered this and repeated this for all possible angles.
S3 Credit
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Now-a-days we can use calculators instead of tables to find the Tan of an angle.
TanOn your calculator press
Notice that your calculator is incredibly accurate!!
Followed by 30, and press =
Accurate to 9 decimal places!
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TrigonometryS3
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What’s the point of all this???
Don’t worry, you’re about to find out!
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TrigonometryS3
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12 m
How high is the tower?
Opp
60°
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TrigonometryS3
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60°
12 mAdjacent
Opposite
Copy this!
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TrigonometryS3
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Tan x° =Opp
Adj
Tan 60° =Opp
12
= Opp12 x Tan 60°
Opp =12 x Tan 60° = 20.8m (1 d.p.)
Copy this!
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TrigonometryS3
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So the tower’s 20.8 m high!
Don’t worry, you’ll be trying plenty of examples!!
20.8m
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Trigonometry
Adj
x°
Tan x° =
Opposite
Opp
Adjacent
S3 Credit
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TrigonometryExample
65°
Tan x° =
OppOpp
Adjh
8m Tan 65° =h8
= h8 x Tan 65°
h = 8 x Tan 65° = 17.2m (1 d.p.)
S3 Credit
Find the height h
SOH CAH TOA
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TrigonometryS3
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Class GroupIdentifying the
Tan Ratio Ex 3.1 & Ex4.1
MIA Page 203
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Starter Questionsw
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22 3 2
1. Find the area and perimeter
of the circle.
2. Is the triangle right angled at P.
Explain your answer.
3. Factorise x x
10cm
P
Q
R
6cm
7cm
10cm
S3 Credit
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7-Sep-14 Created by Mr. Lafferty Maths Dept.
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Learning Intention Success Criteria
2. Use tan of an angle to solve problems.
1. To use tan of the angle to solve problems.
Angles & Triangles
1. Write down tan ratio.
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Using Tan to calculate angles
S3 Credit
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Trigonometry
1812
Example
x°
Tan x° =
Opp
Opp
Adj
SOH CAH TOA
12m Tan x° =
= 1.5Tan x°
18m
S3 Credit
Calculate the tan xo ratio
Q
P
R
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TrigonometryS3
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= 1.5Tan x°
How do we find x°?
We need to use Tan ⁻¹on the calculator.
2nd
Tan ⁻¹is written above Tan
Tan ⁻¹
To get this press TanFollowed by
Calculate the size of angle xo
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TrigonometryS3
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x = Tan ⁻¹1.5 = 56.3° (1 d.p.)
= 1.5Tan x°
2nd Tan
Tan ⁻¹
Press
Enter =1.5
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TrigonometryS3
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Process
1. Identify Hyp, Opp and Adj
2. Write down ratio Tan xo = Opp
Adj
3. Calculate xo 2nd Tan
Tan ⁻¹
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TrigonometryS3
Credit
Now tryExercise 4.2
MIA Page 205
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Starter Questionsw
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1. True or false 30 5 + 6 4 = 48
2. Write in scientific notation 0.0456
3. Identify the sides of the triangle.
4. The subway train takes 6 mins to travel
between 2 stations 3 miles apar
t.
Show that it's average speed is 30mph.
S3 Credit
xo
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7-Sep-14 Created by Mr. Lafferty Maths Dept.
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Learning Intention Success Criteria
2. Use tan of an angle to solve REAL LIFE problems.
1. To use tan of the angle to solve REAL LIFE problems.
Angles & Triangles
1. Write down tan ratio.
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TrigonometryS3
Credit
SOH CAH TOA
7-Sep-14 Compiled by Mr. Lafferty Maths Dept.
Use the tan ratio to find the height h of the treeto 2 decimal places.
47o
8m
rod
o opp htan 47 = =
adj 8
o htan 47 =
8
oh = 8× tan 47
h = 8.58m
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TrigonometryS3
Credit
6o
7-Sep-14Compiled by Mr. Lafferty Maths
Dept.
Aeroplane
a = 15
c
LennoxtownAirport
Q1. An aeroplane is preparing to land at Glasgow Airport. It is over Lennoxtown at present which is 15km from the airport. The angle of descent is 6o.
What is the height of the plane ?
Example 2
o htan 6 =
15
oh = 15× tan 6
h =1.58km
SOH CAH TOA
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TrigonometryS3
Credit
Now tryExercise 5.1
MIA Page 207
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Starter Questionsw
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1. Explain why 6 + 9 3 = 9 and not 5
2. Write in scientific notation 32.56
3. Identify the sides of the triangle.
4. The train takes 10 mins to travel
between 2 stations 6miles apart.
Find the average speed of the train.
S3 Credit
xo
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7-Sep-14 Created by Mr. Lafferty Maths Dept.
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Learning Intention Success Criteria
2. Use tan of an angle to solve find adjacent length.
1. To use tan of the angle to find adjacent length.
Angles & Triangles
1. Write down tan ratio.
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TrigonometryS3
Credit
7-Sep-14 Compiled by Mr. Lafferty Maths Dept.
Use the tan ratio to calculate how far the ladder is away from the building.
45o
12mladder
o opp 12tan 45 = =
adj d
o
12d =
tan 45
d =12m
d m
SOH CAH TOA
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TrigonometryS3
Credit
6o
7-Sep-14 Compiled by Mr. Lafferty Maths Dept.
Aeroplane
a = 1.58 km
LennoxtownAirport
Q1. An aeroplane is preparing to land at Glasgow Airport. It is over Lennoxtown at present. It is at a height of 1.58 km above the ground. It ‘s angle of descent is 6o.
How far is it from the airport to Lennoxtown?
Example 2
o 1.58tan 6 =
d
o
1.58d =
tan 6
d =15 km
SOH CAH TOA
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TrigonometryS3
Credit
Now tryExercise 5.2
MIA Page 210
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Starter Questionsw
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3 3 51. +
4 5 7
2. Explain why y =6 when a = (-1) b = 2
y = (a -b)(b - a)(2a -b)
pQ3. Given T =k .
v Find k when T =6 P = 18 and v =9.
S3 Credit
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7-Sep-14 Created by Mr. Lafferty Maths Dept.
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Learning Intention Success Criteria
2. Use tan ratio to find an angle.
1. To show how to find an angle using tan ratio.
Angles & Triangles
1. Write down tan ratio.
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TrigonometryS3
Credit
7-Sep-14 Compiled by Mr. Lafferty Maths Dept.
Use the tan ratio to calculate the angle that the support wire makes with the ground.
xo
11m
o opp 11tan x = =
adj 4
11
4
o -1x = tan
o ox = 70
4 m
SOH CAH TOA
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TrigonometryS3
Credit
7-Sep-14 Compiled by Mr. Lafferty Maths Dept.
Use the tan ratio to find the angle of take-off.
xo 88m
o opp 88tan x = =
adj 500
otan x = 0.176
o -1 ox = tan (0.176) = 10
500 m
SOH CAH TOA
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TrigonometryS3
Credit
Now tryExercise 6.1
MIA Page 211
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Starter Questionsw
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1. A train takes 12 minutes to travel between 2 stations.
Show that the average speed is 60km/hr
if the stations are 6miles apart.
2. Calculate A when w= (-3) y = 4
A = (w - y) + (y - w)
S3 Credit
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7-Sep-14 Created by Mr. Lafferty Maths Dept.
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Learning Intention Success Criteria
2. Use sine ratio to find an angle.
1. Definite the sine ratio and show how to find an angle using this ratio.
Angles & Triangles
1. Write down sine ratio.
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TrigonometryThe Sine Ratio
x°
Sin x° =
Opposite
OppHyp
S3 Credit
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TrigonometryExample
34°Sin x° =OppOpp
Hyp
h 11cm
Sin 34° =h11
= h11 x Sin 34°
h = 11 x Sin 34° = 6.2cm (1 d.p.)
S3 Credit
Find the height h
SOH CAH TOA
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Using Sin to calculate angles
S3 Credit
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TrigonometryExample
x°
Sin x° =
Opp
Opp
Hyp
6m 9m
Sin x° =69
= 0.667 (3 d.p.)Sin x°
S3 Credit
Find the xo
SOH CAH TOA
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TrigonometryS3
Credit
=0.667 (3 d.p.)Sin x°
How do we find x°?
We need to use Sin ⁻¹on the calculator.
2nd
Sin ⁻¹is written above SinSin ⁻¹
To get this press SinFollowed by
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TrigonometryS3
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x = Sin ⁻¹0.667 = 41.8° (1 d.p.)
= 0.667 (3 d.p.)Sin x°
2nd Sin
Sin ⁻¹
Press
Enter =0.667
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TrigonometryS3
Credit
Now tryExercise 7.1
MIA Page 212
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Starter Questionsw
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1 2 31. Explain why we can simply pick out Q
the 5 figure summary for the data
19, 15, 11, 22, 9, 12, 11
2. Show that the original price of a car is £9000
If it cos
, Q and Q
then find
ts £8100 after a discount of 10%
3. A lorry is travelling at 40mph.
It has travelled 60 miles.
How long has it taken to travel 60 miles.
S3 Credit
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7-Sep-14 Created by Mr. Lafferty Maths Dept.
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Learning Intention Success Criteria
2. Use sine ratio to solve
REAL-LIFE problems.
1. To show how to use the sine ratio to solve
REAL-LIFE problems.
Angles & Triangles
1. Write down sine ratio.
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TrigonometryS3
Credit
SOH CAH TOA
7-Sep-14 Compiled by Mr. Lafferty Maths Dept.
The support rope is 11.7m long. The angle between the rope and ground is 70o. Use the sine ratio to
calculate the height of the flag pole.
70o
h
o opp hsin 70 = =
hyp 11.7
h o= 11.7 sin70
h =11 m
11.7m
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TrigonometryS3
Credit
SOH CAH TOA
7-Sep-14 Compiled by Mr. Lafferty Maths Dept.
Use the sine ratio to find the angle of the ramp.
xo10m
o opp 10sin x = =
hyp 20
o 10sin x =
20
o -1 o10x = sin = 30
20
20 m
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TrigonometryS3
Credit
Now tryExercise 7.2
MIA Page 214
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Starter Questionsw
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2
1. Fill in the ? marks.
2. Calculate A when w= (-10)
A = w
4
x x x x
S3 Credit
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7-Sep-14 Created by Mr. Lafferty Maths Dept.
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Learning Intention Success Criteria
2. Use sine ratio to find the hypotenuse.
1. To show how to calculate the hypotenuse using the sine ratio.
Angles & Triangles
1. Write down sine ratio.
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Trigonometry
SOH CAH TOA
Example
72°
Sin x° =Opp
Hyp
Sin 72° =5
r
r =
r = 5.3 km
5km
S3 Credit
AB
C
r5
sin72o
A road AB is right angled at B. The road BC is 5 km.
Calculate the length of the new road AC.
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TrigonometryS3
Credit
Now tryExercise 8.1
MIA Page 215
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Starter Questionsw
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1 31. Explain why we can simply pick out Q
then find the 5 figure summary for the data
9, 5, 11, 2, 9, 2
2. Find the original price of a football
If it costs £20 after a discoun
and Q
t of 80%
3. A lorry is travelling at 50mph.
It has travelled 75 miles.
Show that the time taken is 1hr 30 mins.
S3 Credit
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7-Sep-14 Created by Mr. Lafferty Maths Dept.
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Learning Intention Success Criteria
2. Use cosine ratio to find a length or angle.
1. Definite the cosine ratio and show how to find an length or angle using this ratio.
Angles & Triangles
1. Write down cosine ratio.
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TrigonometryThe Cosine Ratio
Cos x° =
Adjacent
Adj
x°
Hyp
S3 Credit
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Trigonometry
SOH CAH TOA
Example
40°
Cos x° = Opp
Adj
Hyp
b
35mm
Cos 40° =b
35
= b35 x Cos 40°
b = 35 x Cos 40°= 26.8mm (1 d.p.)
S3 Credit
Find the adjacent length b
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Using Cos to calculate angles
S3 Credit
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Trigonometry
SOH CAH TOA
Example
x°Cos x° = O
pp
Adj
Hyp45cm
Cos x° =3445
= 0.756 (3 d.p.)Cos x°
x = Cos ⁻¹0.756 =41°
34cm
S3 Credit
Find the angle xo
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TrigonometryS3
Credit
Now tryExercise 9.1
MIA Page 216
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Starter Questionsw
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o
1. Calculate 104 x 100
putting your answer in standard form.
2. Is this triangle right angled ?
If yes, find the size of angle x .
If no find the area of the triangle.
S3 Credit
xo
6
8
10
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The Three Ratios
Cosine
Sine
Tangent
Sine
Sine
Tangent
Cosine
Cosine
Sine
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S3 Credit
opposite
opposite opposite
adjacent
adjacent
adjacent
hypotenuse
hypotenuse
hypotenuse
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Trigonometry
Sin x° =Opp
HypCos x° =
Adj
HypTan x° =
Opp
Adj
CAH TOASOH
S3 Credit
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Trigonometry
SOH CAH TOA
Copy this!
S3 Credit
1. Write down
Process
Identify what you want to find
what you know3.
2.
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TrigonometryPast Paper Type Questions
S3 Credit
SOH CAH TOA
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TrigonometryPast Paper Type Questions
S3 Credit
(4 marks)
SOH CAH TOA
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TrigonometryPast Paper Type Questions
S3 Credit
SOH CAH TOA
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TrigonometryPast Paper Type Questions
S3 Credit
SOH CAH TOA
4 marks
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TrigonometryPast Paper Type Questions
S3 Credit
SOH CAH TOA
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TrigonometryPast Paper Type Questions
S3 Credit
(4marks)
SOH CAH TOA
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TrigonometryPast Paper Type Questions
S3 Credit
SOH CAH TOA
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TrigonometryPast Paper Type Questions
S3 Credit
(4marks)
SOH CAH TOA
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Trigonometry
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Trigonometry
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TrigonometryS3
Credit
Now try Exercise 10.1 & 10.2
MIA Page 218