Question

Решите уравнение
cos2 x - 11cosx+10=0

Answer 1

$cos^2x-11cosx+10=0 \\ cosx=y \\ y^2-11y+10=0 \\ D=81 \\ y_1=1 \\ y_2=10 \\ \\ cosx=1 \\ x=0 \\ \\ cosx=10 \\ x=0$