How to solve $\cos(5\alpha + \pi/2) = \cos(2\alpha + \pi/8)$ for $a$? I missed the lecture. I don't want you to solve my homework, I just want to learn how to solve equations like this one. Since I have no idea, I'll post the task I got for homework, rather than obfuscating it beyond recognition. Please give general directions on how to solve equations like this one.
$$\cos(5\alpha + \pi/2) = \cos(2\alpha + \pi/8)$$

Use Cos(C) - Cos(D) formula.
U can also solve by graphical method. You know the graph of Cosx then apply transformation to draw LHS and RHS intersection point will be the solution
