Alright, not really homework or coursework.(adsbygoogle = window.adsbygoogle || []).push({});

Sum(from k = 0 to infinity) (cos thetha)^2k = 5

So i subbed in the first value, 0 and took the one out.

I have to find the value of cos(2thetha)

and then there was a pattern, but i didn't really know what to do.

Thanks

P.S. Not really familiar with Latex yet.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Trigo Question - just for fun

**Physics Forums | Science Articles, Homework Help, Discussion**