# How do you find the side length of a decagon?

• In the diagram below the length of AC is 5 feet, the angle ABC has measure 144/2 = 72 degrees and the angle CAB is a right angle. |AB| = 5/tan(72o) = 1.62 feet. Hence the length of a side of the decagon is 2 × 1.62 = 3.24 feet.

• The ten radii divide the decagon into 10 congruent isosceles triangles. This fact is used in deriving the formula for area of a regular decagon. In other words, take the length of a side, square it and multiply by 7.694 to get the area of a decagon.

Similarly, what do you call a 10 sided shape? In geometry, a decagon is a ten-sided polygon or 10-gon.

Correspondingly, what is the formula to find the sides of a polygon?

Subtract the interior angle from 180. For example, if the interior angle was 165, subtracting it from 180 would yield 15. Divide 360 by the difference of the angle and 180 degrees. For the example, 360 divided by 15 equals 24, which is the number of sides of the polygon.

Are of a circle?

The area of a circle is pi times the radius squared (A = π r²). Learn how to use this formula to find the area of a circle when given the diameter.

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