Hi friends,(adsbygoogle = window.adsbygoogle || []).push({});

I am not able to understand how the below shown identity becomes (-1) power v cosθ.

cos(vπ − θ ) = cos vπ cos θ + sin vπ sin θ =(−1)power v cos θ

==> (-1)^{v}cos θ

Please help me understand this basic problem.

Thanks,

Nesta

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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

Dismiss Notice

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: Identity problem

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