Find the area of the regular 30 -gon with radius 7 mm.
A formula to find the area of a regular polygon given the radius is:
Area = r2 · n · sin( 360 / n ) / 2
= 72 · 30 · sin( 360 / 30 ) / 2
= 72 · 30 · sin( 12 ) / 2
= 5.09 mm2 (approximately)
The area is given by :
30 * (1/2) * (7^2) * sin (12°) ≈ 152.8 mm^2
[ I think geno's answer would be the same.....]