2cos^3x-2cos^2x+sin^2x=0

2cos^3 (x) - 2cos^2 (x) + sin^2 (x) = 0

2cos^3 (x) - 2cos^2 (x) + 1-cos^2 (x) = 0

2cos^3 (x) - 3cos^2 (x) + 1=0

2cos^3 (x) - 3cos^2 (x) = - 1

cos^2 (x) (2cos (x) - 3) = - 1

cos^2 (x) = - 1 уравнение тождественно равно

2cos (x) - 3=-1 x=0