Question

cos^3+cos-sin^2cos

Answer 1

how is this sin^2cos ????

or you think

cos^3 x +cos x - sin^2 x * cos x

yes ?

so then rewrite sin^2 x = 1 -cos^2 x then substitute inside equation and note cos x = t so the will get an equation with t

after you get these roots make them equal cos x and will get the needed roots of first equation

hope this will help you