Cos x - 2 sin x/4 * cos x/4 =0

cosx - 2sin(x/4)cos(x/4) = 0 cosx - sin(x/2) = 0 1 - 2sin²(x/2) - sin(x/2) = 0 2sin²(x/2) + sin(x/2) - 1 = 0 sin(x/2) = t 2t² + t - 1 = 0 D = 1 + 4*2*1 = 9 t1 = (- 1 - 3)/4 t1 = - 1 t2 = ( - 1 + 3)/4 t2 = 1/2 1)  sin(x/2) = - 1 x/2 = - π/2 + 2πk, k∈Z x1 = - π + 4πk, k∈Z 2)  sin(x/2) = 1/2 x/2 = (-1)^(n)*arcsin(1/2) + πn, n∈Z x/2 = (-1)^(n)*(π/6) + πn, n∈Z x2 = (-1)^(n)*(π/3) + 2πn, n∈Z