Question

cos5x*cos2x+sin5x*sin2x=0,5 помогите плиз

Answer 1

$cos5xcos2x+sin5xsin2x=0,5 \ cos(5x-2x)=0.5 \ cos3x=0.5 \ 3x=pm frac{pi}{3}+2pi n \ x=pm frac{pi}{9}+ frac{ 2pi n}{3}, nin Z$