How to know how to sketch $\cos^2 x$ graphs from $\cos x$?
I am trying to understand spherical harmonics, but I need to brush up on my fundamentals to understand it faster and better.
For example, $\cos x$ graphs peaks at 0 and $\pi$, but what about $\cos^2 x $ graphs?
How do I understand where it peaks for $\cos^2 x$ ? I've been told to visualise it as $2 cosine graphs, but what does that mean?