Download presentation

Presentation is loading. Please wait.

Published byGyles Stephens Modified over 9 years ago

1
1 of 84 S HAPE AND S PACE Circles

2
2 of 84 L ET US DEFINE C IRCLE A ___________is a simple shape that is the set of all points in a plane that are at a given distance from a given point, the center. A circle is a simple shape that is the set of all points in a plane that are at a given distance from a given point, the center.

3
3 of 84 Radius is the distance from the center to the edge of a circle. Radius is half of the diameter

4
4 of 84 Diameter is a segment that passes through the center and has its endpoints on the circle. The diameter is twice the length of the radius

5
5 of 84 T HE VALUE OF We use the symbol π because the number cannot be written exactly. π = 3.141592653589793238462643383279502884197169 39937510582097494459230781640628620899862803482 53421170679821480865132823066470938446095505822 31725359408128481117450284102701938521105559644 62294895493038196 (to 200 decimal places)!

6
6 of 84 In circles the AREA is equal to 3.14 ( ) times the radius (r) to the power of 2. Thus the formula looks like: A= r 2 In circles the circumference is formula looks like: 2 r The circumference of a circle is the actual length around the circle which is equal to 360°. π is equal to 3.14.

7
7 of 84 T HE CIRCUMFERENCE OF A CIRCLE Use π = 3.14 to find the circumference of this circle. C = 2 πr 8 cm = 2 × 4 = 8 π R = 4

8
8 of 84 T HE CIRCUMFERENCE OF A CIRCLE Use π = 3.14 to find the circumference of the following circles: C = 2 πr 4 cm = 2 × 2 = 4 π cm C = 2 πr 9 m = 2 × π × 9 = 18 π m C = 2 πr = 2 × 12 = 12 π mm C = 2 πr 58 cm = 2 × π × 58 = 116 π cm 24mm

9
9 of 84 F ORMULA FOR THE AREA OF A CIRCLE We can find the area of a circle using the formula radius Area of a circle = πr 2 Area of a circle = π × r × r or

10
10 of 84 A REA OF A CIRCLE

11
11 of 84 T HE CIRCUMFERENCE OF A CIRCLE Use π = 3.14 to find the area of this circle. A = πr 2 4 cm = π × 4 × 4 = 16 π cm 2

12
12 of 84 T HE AREA OF A CIRCLE Use π = 3.14 to find the area of the following circles: A = πr 2 2 cm = π × 2 2 = 4 π cm 2 A = πr 2 10 m = π × 5 2 = 25 π m 2 A = πr 2 23 mm = π × 23 2 = 529 π mm 2 A = πr 2 78 cm = π × 39 2 = 1521 π cm 2

13
13 of 84 F IND THE AREA OF THIS SHAPE Use π = 3.14 to find area of this shape. The area of this shape is made up of the area of a circle of diameter 12cm and the area of a rectangle of width 6cm and length 12cm. 6 cm 12 cm Area of circle = π × 6 2 = 36 π cm 2 Area of rectangle = 6 × 12 = 78 cm 2 Total area = 36 π + 78

14
14 of 84 ? F INDING THE RADIUS GIVEN THE CIRCUMFERENCE Use π = 3.14 to find the radius of this circle. C = 2 πr 12 cm How can we rearrange this to make r the subject of the formula? r = C 2π2π 12 2 × π = 6 π =

15
15 of 84 F IND THE PERIMETER OF THIS SHAPE Use π = 3.14 to find perimeter of this shape. The perimeter of this shape is made up of the circumference of a circle of diameter 13 cm and two lines of length 6 cm. 6 cm 14 cm Perimeter = 14 x 6 Circumference = 2 πr

16
16 of 84 C IRCUMFERENCE PROBLEM The diameter of a bicycle wheel is 50 cm. How many complete rotations does it make over a distance of 1 km? 50 cm The circumference of the wheel = π × 50 Using C = 2 πr and π = 3.14, = 157 cm

Similar presentations

© 2024 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google