Circle
From Wikipedia, a free encyclopedia written in simple English for easy reading.
A circle is a round shape, such as the letter o.
The diameter (meaning "all the way across"), or d, of a circle is equal to twice its radius. (d equals 2 times r, or d=2r). 'Diameter' means a straight line that goes from one side to the opposite and right through the point in the very middle.
The number pi, usually written using its symbol π, equal to about 22/7ths or 3.14159, is very useful for getting information about a circle:
- The circumference (c) (meaning "all the way around") of a circle is equal to π times the diameter. (c equals π times d, or c=πd)
- The area bounded by a circle (a) is equal to the radius multiplied by itself, then multiplied by π. (a equals π times (r times r), or a=πr^2)
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Circle
