Find all solutions

Assuming that you mean 2 sin x cos x - cos x = 0.

In that case you can factor out cos x.

(2 sin x - 1) cos x = 0

so either cos x = 0 so that x = nπ + π/2 is a solution for every integer n, or sin x = 1/2 in which case 2nπ + π/6 and 2nπ + 5π/6 are solutions for every integer n.

These are all the solutions.

In degrees, these answers would be 180n+90, 360n+30, and 360n+150, again for all integers n.