



 
Hi Lewis, I assume you mean a regular octagon where all the sides have the same length and all the angles have the same measure. In my diagram the diameter is d and the side length is s. From the diagram you can see that
Since you know that s = 60 feet all that remains is to find x. This we can do using Pythagoras Theorem. The small triangles with sides of length x, x and s are right triangles so, using Pythagoras Theorem,
so
Thus
In your case s = 60 feet so
Penny  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 