Question

2sin²(π/4-7a)-1
госпаде памаги памилуй​

Answer 1

$2Sin^{2}(\frac{\pi }{4} -7\alpha)-1=-[ 1-2Sin^{2}(\frac{\pi }{4} -7\alpha)] =-Cos(2(\frac{\pi }{4}-7\alpha)) =\\\\=-Cos(\frac{\pi }{2}-14\alpha)=\boxed{-Sin14\alpha}$