Question

Найдите значение выражения:[tex]4\sqrt{2} cos\frac{\pi }{4} cos\frac{7\pi }

Answer 1

$4\sqrt{2} cos\frac{\pi }{4} cos\frac{7\pi}{3}=4\sqrt{2}*\frac{\sqrt{2}}{2}Cos(2\pi+\frac{\pi}{3}) =4Cos\frac{\pi}{3}=4*\frac{1}{2}=2$