Question

Спростить выраз
(sin9a/sin3a - cos9a/cos3a)-2

Answer 1

$\bigg(\displaystyle \frac{\sin9\alpha}{\sin3\alpha}-\frac{\cos9\alpha}{\cos3\alpha}\bigg)-2=\frac{\sin9\alpha\cos3\alpha-\cos9\alpha\sin3\alpha}{\sin3\alpha\cos3\alpha}-2=\\ \\ \\ =\frac{\sin(9\alpha-3\alpha)}{0.5\sin6\alpha}-2=\frac{2\sin6\alpha}{\sin6\alpha}-2=2-2=0$