Math CentralQuandaries & Queries


Question from brandon, a student:

what are the area and perimeter and area of half a circle??

Hi Brandon,

The area of a circle is π r2 square units where r is the radius of the circle, so the area of half a circle is half of that.

The circumference of a circle is 2 π r units so half way around the circle would be 2 π r/2 = π r units. The perimeter of half a circle however includes the curved part of length π r units and the diameter of length 2 r so the perimeter is π r + 2 r.


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