Question

Упростить выражение cosa-cos5a/sin5a+sina

Answer 1

$frac{cosa-cos5a}{sin5a+sina} = frac{-2*sin frac{5a+a}{2}*sin frac{a-5a}{2} }{2*sin frac{a+5a}{2}*cos frac{5a-a}{2} }}= frac{-2*sin3a*(-sin2a)}{2*sin3a*cos2a} = frac{sin2a}{cos2a} =tg2a$