Question

Помогите, пожалуйста!!!

Answer 1

$frac{2}{sqrt{3}}(Sin^{4}15^{o}-Cos^{4}15^{o})=frac{2}{sqrt{3}}(Sin^{2}15^{o}+Cos^{2}15^{o})(Sin^{2}15^{o}-Cos^{2}15^{o})=frac{2}{sqrt{3}}*1*(-Cos30^{o})=-frac{2}{sqrt{3}}*frac{sqrt{3}}{2}=-1\\Otvet:boxed{-1}$