Question

.........задания на фото

Answer 1

$1)8sqrt{3}Cos^{2} frac{7pi }{12}-8sqrt{3}Sin^{2}frac{7pi }{12}=8sqrt{3}(Cos^{2}frac{7pi }{12} -Sin^{2}frac{7pi }{12})=8sqrt{3}Cos(2*frac{7pi }{12})=8sqrt{3}Cosfrac{7pi }{6}=8sqrt{3}Cos(pi+frac{pi }{6})=8sqrt{3}*(-Cosfrac{pi }{6})=-8sqrt{3}*frac{sqrt{3} }{2}=-12$

$2)8sqrt{3}-8sqrt{12}Sin^{2} frac{5pi }{12}=8sqrt{3}-8sqrt{4*3}Sin^{2}frac{5pi }{12}=8sqrt{3}-16sqrt{3}Sin^{2}frac{5pi }{12} =8sqrt{3}(1-2Sin^{2}frac{5pi }{12})=8sqrt{3}*Cos(2*frac{5pi }{12}) }=8sqrt{3}Cosfrac{5pi }{6} =8sqrt{3} Cos(pi- frac{pi }{6})=8sqrt{3}*(-Cosfrac{pi }{6})=-8sqrt{3}*frac{sqrt{3} }{2}=-12$

$3)-95Cos2alpha=-95*(2Cos^{2}alpha-1)=-95(2*(-0,6)^{2}-1)=-95*(0,72-1)=-95*(-0,28)=2,66$