CIRCLE

Introduction

-2-dimension

-Circular geometry shape

- Set of all point in the plane

A circle is…

Constructing a Circle

Compass is use to create a Perfect Circle with accurate measurements

-To make sure the r (radius) and the d (diameter) are the same at all points

CircleArc-A closed segment of a curve

Sector-A region of a circle which is "cut off" from the circle by a chord

Segment-A portion of a disk enclosed by two radii and an arc

CircleRadius-A distance from the center of the circle to any point of the circumference

Diameter-A distance between two point passing through the center

Circumference-Linear distance around the edge of a closed curve

Piiiiiiii…

Do You Know…Pi is a irrational number since its value is not proportion

Pi has 18 digit decimal place

-which is 3.141592653589793238

Circumference

In which π=22/7 or 3.142

-C=2πr or πd

CircumferenceExample: You walk around a circle which has a diameter of 100m, how far have you walked?

Distance walked = Circumference = π × 100m= 314m (to the nearest m)

-Using the formula of πd

Arc Length

s=arc length of the circle

r=radius

0=degree/radian (converted)

Arc, s=r0

Arc Length

s=r0

s=9(1.05 rad)

s=9.424 cm

Example:

Area of the Sector

s=sector of the circle

r=radius

0=degree/radian

Area of the Sector

s=1/2r2 0

s=1/2(24) 2 (2.095 rad)

s=603.072 cm2

Example:

Area of the SegmentArea of Segment=Area of sector-Area of triangle

r2(0-sin 0)r=radius

0=degree/radian

Area of the Segment

s=1/2r2 (0-sin 0)

s=1/2(7) 2 (1.746 rad)-sin (1.746 rad)

s=42.01 cm2

Example:

SPHERE

Introduction

A sphere is…-3 Dimension

-Circular in shape

-Rounded ball surface completely

Surface Area

A=4πr2

A=Surface area

r =Radius

Surface Area

A=4πr

A=4(22/7)(5) 2

A=314.29cm2

Volume

V= πr3V=Volume

r=radius

Volume

V=4/3 (22/7)(8)3

V=2145.52cm3