Inscribed and described circle

Find the radii of a circle inscribed and circumscribed by a regular pentagon whose side measures 3 cm.

Correct result:

r =  2.0646 cm
R =  2.552 cm


a=3 cm n=5 α=π/n=3.1416/50.6283 rad  r=a2 tan(α)=32 tan(0.6283)=2.0646 cm
R=a2 sin(α)=32 sin(0.6283)=2.552 cm

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