Question

Решите уравнение 2cos²x - cosx=0

Answer 1

$2cos^2x - cosx=0 \cosx=y \2y^2-y=0 \y(2y-1)=0 \y_1=0 \2y=1 \y_2= frac{1}{2} \cosx=0 \x_1= frac{pi}{2} +pi n, n in Z \cosx= frac{1}{2} \x_{2,3}=pm frac{pi}{3}+2pi n , n in Z$