Simplify:

1. sinx cos2x / cosx sin2x

sinx cos^{2}x - sin^{2}x / 2 sinx cosx

sinx ( cos^{2}x - 1) / 2 sinx cosx

solution: 1 - 1/2 cos^{2}x

I am not sure if what I did is right and I don't know what to do next. May you help me?? Thanks for the answers.