



 
Molly, I think the expression you are using is where a is the length of a side and n is the number of sides. To evaluate the denominator use the tan button on your calculator. For example for an octagon where n = 8, 360^{o}/(2n) = 360^{o}/16 = 22.5^{o}. Make sure your calculator is in degree mode not radian mode, and evaluate tan(22.5^{o}). I got tan(22.5^{o}) = 0.414214. Thus the denominator is 4 tan(22.5) = 4 × 0.414214 = 1.6569. I hope that helps,  


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