



 
Hi Cody, I'm going to assume you mean a regular octagon. Are you looking for the length of AB, the red line in the diagram?
If so, then since ABC is a right triangle you can use Pythagoras theorem. You know the length of CA is 3 feet so all that remains is to find the length of BC. Look at the first diagram in my response to a previous question. The length of BC is W  2b in that diagram. Can you complete the problem from here? Penny  


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