Question

Доказать тождество

Answer 1

$...=frac{2cos3 alpha +(sin4 alpha -sin2 alpha )}{-2sin3 alpha +(cos4 alpha -cos2 alpha )}=frac{2cos3 alpha +2sin alpha cdot cos3 alpha }{-2sin3 alpha -2sin3 alpha cdot sin alpha }=\\=frac{2cos3 alpha (1+sin alpha )}{-2sin3 alpha (1+sin alpha )}=-frac{cos3 alpha }{sin3 alpha }=-ctg3 alpha$