Question

докажите 4sinacos^3a-2sin2asin^2a=sin4a

Answer 1

4sinacos^3a-4sinacosa*sin^2a=
=4sinacos^3a-4sin^3acosa=4sinacosa(cos^2a-sin^2a)=2sin2a*cos2a=sin4a
ч.т.д.