# Math Help - About the golden ratio

1. ## About the golden ratio

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

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

2. ## Re: About the golden ratio

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