Question

Решите пример
cos(-25п/3)+sin(-9п/4)+ctg 7П/2

Answer 1

$cos(-\frac{25\pi }{3})+sin(-\frac{9\pi }{4})+ctg\frac{7\pi }{2}=\\\\=cos(8\pi +\frac{\pi }{3})-sin(2\pi +\frac{\pi }{4})+ctg(3\pi +\frac{\pi }{2})=cos\frac{\pi }{3}-sin\frac{\pi }{4}+ctg\frac{\pi }{2} =\\\\=\frac{1}{2}-\frac{\sqrt2}{2}+0=\frac{1-\sqrt2}{2}$