looks like it to me.
cos^3x - cosx = 0
cosx (cosx-1)(cosx+1) = 0
Oops. Looks like you left out where cosx=0.
Find the solutions for this equation in the interval [0, 2pi).
cos^3 x = cos x
Are they 0 and pi?
2 answers
0, pi/2, pi, and 3pi/2?