Question

Помогите решить 4sin^2(a) - 4sin^4(a) = din^2(2a)

Answer 1

$4sin^2a-4sin^4a=sin^22a\\4sin^2a(1-sin^2a)=(2sinacdot cosa)^2\\4sin^2a(1-sin^2a)=4sin^2acdot cos^2a\\4sin^2acdot cos^2a=4sin^2acdot cos^2a; -quad vernoe; ravenstvo\\Tozdestvo; dokazano.$