# About the golden ratio

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• July 3rd 2011, 02:14 AM
scounged
About the golden ratio
Is this equality valid? I just noticed it, and I haven't heard of it before.

$2cos(\frac{\pi }{5})=\varphi,~where~\varphi~is~the~golden~ratio.$
• July 3rd 2011, 02:33 AM
mr fantastic
Re: About the golden ratio
Quote:

Originally Posted by scounged
Is this equality valid? I just noticed it, and I haven't heard of it before.

$2cos(\frac{\pi }{5})=\varphi,~where~\varphi~is~the~golden~ratio.$

Found using Google in t < 60 seconds:

http://www.theproblemsite.com/thegol...igonometry.asp

Golden ratio and special angles — The Endeavour