9514 1404 393
Answer:
9.404 cm
Explanation:
A regular polygon with n sides inscribed in a circle of radius r will have a side length given by ...
s = 2r·sin(180°/n)
For r = 8 and n = 5, this gives a side length of ...
s = 2·8·sin(180°/5) = 16·sin(36°) ≈ 9.404 . . . cm