ОЧЕНЬ СРОЧНО!!!!!!!!!!!!!!

Решите задачу:

$1)4\sqrt{3}Sin(-120^{o})=4\sqrt{3}*(-\frac{\sqrt{3} }{2})=-2*3=-6\\\\2)\alpha\in1chetverti\\\\Sin\alpha=\sqrt{1-Cos^{2}\alpha}=\sqrt{1-(\frac{2\sqrt{6}}{5})^{2}}=\sqrt{1-\frac{24}{25}} =\sqrt{\frac{1}{25} }=\frac{1}{5}=0,2$

$3)Sin\frac{\pi }{2}+Sin\frac{3\pi }{2}=1-1=0\\\\4)14\sqrt{6}Cos\frac{19\pi }{6}*Cos\frac{7\pi }{4}=14\sqrt{6}Cos(3\pi+\frac{\pi }{6})Cos(2\pi -\frac{\pi }{4})=14\sqrt{6}*(-Cos\frac{\pi }{6})Cos\frac{\pi }{4}=-14\sqrt{6}*\frac{\sqrt{3} }{2}*\frac{\sqrt{2} }{2}=-\frac{14*6}{4} =-21$