Question

Докажите тождество:
((sin5a-sin3a)/2cos4a)=sina

Answer 1

$frac{sin 5 alpha -sin 3 alpha }{2cos 4 alpha } = dfrac{2sin frac{5 alpha -3 alpha }{2}cdot cos frac{5 alpha +3 alpha }{2} }{2cos 4 alpha } = frac{2sin alpha cdot cos 4 alpha }{2cos 4 alpha } =sin alpha$