Question

Упростить выражение cosa-cos5a/sin5a+sina

Answer 1

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