Question

Решите уравнение ===========>

Answer 1

$4sin^2x-cos x-1=4-4cos^2x-cosx-1=0\cosx=t\4t^2+t-3=0\D=49\t_1={3over4}\t_2=-1\\x_1=pm arccos{3over4}+2pi k,kin Z\x_2=pi+2pi k, kin Z$