Decagon

Calculate the area and circumference of the regular decagon when its radius of a circle circumscribing is R = 1m

Correct result:

S =  2.9389 m2
o =  6.1803 m

Solution:

R=1 m n=10  A=360/n=360/10=36  sinA/2=a/2R  a=2 R sin(A/2)=2 1 sin(36/2)0.618 m  r=R2(a/2)2=12(0.618/2)20.9511 m  S1=r a2=0.9511 0.61820.2939 m2 S=n S1=10 0.2939=2.9389 m2
o=n a=10 0.618=6.1803 m



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