Hey,

I was going through my textbook, and came across this challenge question:

Solve $\displaystyle \int{\cos^2{x}dx}$ without using the half-angle formula.

I've been running through every trig identity I know, trying to figure out a way to simplify this. Does anyone have an idea? It's trivial to solve using the half-angle formula. I've been racking my brain and can't figure out a way to solve the question without it.