Question

Помогите с решением,,,,,,,

Answer 1

$1)14Sin\frac{7\pi }{12}*Cos\frac{7\pi }{12} =7*(2Sin\frac{7\pi }{12}Cos\frac{7\pi }{12})=7*Sin(2*\frac{7\pi }{12})=7Sin\frac{7\pi }{6}=7Sin(\pi +\frac{\pi }{6})=7*(-Sin\frac{\pi }{6})=7*(-\frac{1}{2})=-3,5$

$2)8\sqrt{3}Cos^{2} \frac{7\pi }{12}-8\sqrt{3}Sin^{2}\frac{7\pi }{12}=8\sqrt{3}(Cos^{2}\frac{7\pi }{12} -Sin^{2}\frac{7\pi }{12})=8\sqrt{3}Cos(2*\frac{7\pi }{12})=8\sqrt{3}Cos\frac{7\pi }{6}=8\sqrt{3}Cos(\pi+\frac{\pi }{6})=8\sqrt{3}*(-Cos\frac{\pi }{6})=-8\sqrt{3}*\frac{\sqrt{3} }{2}=-12$