Question

sin^2x+cos2x-cosx=0

Answer 1

The best way to solve this is to use the identity \(\cos(2x) = \cos^2x - \sin^2x\)

Answer 2

Because if you substitute \(\cos(2x)\) you would have

\(\sin^2x + \cos^2x - \sin^2x - \cos x = 0\)

The \(\sin^2x\) cancels leaving just

\(\cos^2x - \cos x = 0\)

Which factors to
\(\cos x(\cos x - 1) = 0\)

And simplifies to
\(\cos x = 0\)
\(\cos x = 1\)

I hope this helps