# revision notes for circumference of a circle

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- Created by: annum
- Created on: 09-02-13 18:19

First 141 words of the document:

Circumference of a circle

The circumference is the length of the edge around a circle.

For any circle, the circumference is:

3.14... × the diameter.

The diameter is worked out by the diameter is equal to 2 × radius, (2r), so we can also write this formula as:

C = 2r

You work out the radius by dividing the diameter by 2

C = circumference

A = area

D = diameter

R = radius

The perimeter of a semi-circle can be found by using the equation x r², which is commonly

used to calculate the area of a whole circle:

area of a semi-circle: 1/2 x x r2

area of a quarter circle: 1/4 x x r2

perimeter of a semi-circle: x r + 2 x r

perimeter of a quarter circle: 1/2 x x r + 2 x r

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