Date: May 30, 2013 1:46 AM
Author: RGVickson@shaw.ca
Subject: Re: Trying to find perimeter of a regular pentagon

On Tuesday, May 28, 2013 8:15:05 AM UTC-7, 130bcd wrote:
> Hello,
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> I have unsuccessfully tried to find the perimeter of a pentagon. The "radius" to the vertices is 130, which I tried to convert into 5 triangles but I can't find a formula for determining the length of the 3rd side of an isosceles triangle.
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> The two equal length sides would, of course be 130 and the angle between them would be 72.
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> Help, please!


Check out the explanatory article in

http://www.math.iastate.edu/thesisarchive/MSM/EekhoffMSMSS07.pdf

It derives all the formulas you need.