



 
Hi Susan, I assume you want a regular octagon. If you look at our page on finding the area of a regular polygon you will see a formula that Stephen developed that uses the length of a side $a$ and the number of sides $n.$ the expression is \[A_T = \frac{a^2 n}{4 \tan\left(\frac{360^o}{2 n}\right)}\] If you want the area to be 800 square feet then this gives \[800 = \frac{8 \times a^2 }{4 \tan\left(\frac{360^o}{16}\right)}.\] Use your calculator to calculate $\tan\left(\frac{360^o}{16}\right)$ and then solve for $a.$ Write back if you need more assistance. Penny  


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