Cos2x=sin^2 x 1 – 2sin^2x – sin^2x = 0 -3sin^2x = - 1 3sin^2x = 1 sinx = ± sqrt(3)/3 1) sinx = sqrt(3)/3 x = (-1)^k * arcsin(√3/3) + pik, k ∈ Z 2) sinx = - sqrt(3)/3 x = (-1)^(k+1) * arcsin(√3/3) + pik, k ∈ Z