Question 29601
In a regular polygon, the length of one side, s, is given by{{{2Rsin(180/n)}}} where:
s = the length of one side.
R = The distance from the centre to one vertex. This is the same as the radius of the circumscribed circle, or 15.8
n = The number of sides in the regular polygon. For this problem, we have an octagon, so n = 8.

{{{s = 2(15.8)sin(180/8)}}}
{{{s = 31.6sin(22.5)}}}
{{{s = 31.6(0.38)}}}
{{{s = 12.1}}}

The perimeter, P, of the regular octagon is n*s
{{{P = 8(12.1)}}}
{{{P = 96.8}}}