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A Regular Polygon with 12 sides: Area, Perimeter, Interior and Exterior Angles, Inradius, Circumradius



A regular polygon with 12 sides where the length of each side is 6 units. The units may either be inches or cm or km or miles: any unit of length.

You are given a Regular Polygon with 12 sides. What are the interior angles and exterior angles? 
If the length of each side is 6 units, what is the perimeter, area, circum-radius and in-radius of the polygon?

n = 12

Perimeter of a polygon with 12 sides = (side length) x 12 = 72 units

Area of a polygon with 12 sides = (n x Sidecot (Π/n))/4 = (n x 6cot (Π/12))/4 = 403.06 square units

Sum of the interior angles of a polygon with 12 sides = 
 (n-2) x 180 degrees =  (12-2) x 180 degrees = 1800 degrees

Interior Angle of a polygon with 12 sides = (n-2) x 180/n degrees = (12-2) x 180/12 degrees = 150 degrees 

Exterior angle of a polygon with 12 sides = 180 - Interior Angle = 180 - 150 = 30 degrees

Inradius = Radius of In-circle = (side length) x cot (Π/12) = 6 x cot 15 = 22.39 units

Circumradius = Radius of Circum-circle = (side length) x cosec (Π/12) = 6 x cosec 15 degrees = 23.18 units

Symmetry Group = D12  12 rotational symmetries and 12 reflection symmetries. The "D" stands for di-hedral. 




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