Question

И снова помогите с триганометрией. 20 баллов.

Answer 1

$1)-7Cos2\alpha=-7(1-2Sin^{2}\alpha)=-7(1-2*0,5^{2})=-7(1-0,5)=-7*0,5=-3,5\\\\2)\frac{3Sin4\alpha}{5Cos2\alpha}=\frac{3*2Sin2\alpha Cos2\alpha}{5Cos2\alpha}=\frac{6Sin2\alpha}{5}=1,2Sin2\alpha=1,2*(-0,2)=-0,24$