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Parts of a circle

The geometry of a circle

The diameter of a circle is the distance across the circle at the widest part of the circle. The diameter is always equal to twice the radius of the circle, because the radius starts from the center of the circle and goes straight to the edge.

Learn by doing: measure the diameter of some circles in your house
Radius
Area of a Circle
More about Geometry

Bibliography and further reading about circles:

  

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