Regular polygon area from circumcircle

Calculates the area of the circumcircle and of the regular polygon from radius of circumcircle and number of sides

Area of a regular polygon is the sum of area of a triangles it contains. Area of a triangle is
where a and b - triangle sides, and gamma is angle between those sides. For triangle in regular polygon a and b are circumradius, and gamma is 360/n, where n - number of sides. Thus area of polygon is
Calculator also displays area of the circumcircle, for reference
S=\pi r^2

PLANETCALC, Regular polygon area from circumcircle

Regular polygon area from circumcircle

Digits after the decimal point: 2
Polygon area
Circumcircle area
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