Area of a Circle - Geometry Made Easy
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Area of a Circle

Radius

The area of a circle is the flat surface inside its circumference. The area is always equal to the radius squared, multiplied by π (pi).

Here's a proof that this is always true for any circle.

Learn by doing: figure out the area of some circles around you.
Radius
Diameter
Circumference of a Circle
More about Geometry

Bibliography and further reading about circles:

More about Geometry
More about Math
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Professor Carr

Karen Eva Carr, PhD.
Assoc. Professor Emerita, History
Portland State University

Professor Carr holds a B.A. with high honors from Cornell University in classics and archaeology, and her M.A. and PhD. from the University of Michigan in Classical Art and Archaeology. She has excavated in Scotland, Cyprus, Greece, Israel, and Tunisia, and she has been teaching history to university students for a very long time.

Professor Carr's PSU page

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