ответ. ((3^0,5)/2)*((cos(75))^4-(cos(15))^4)=((3^0,5)/2)*((sin(15))^2-(cos(15))^2)*((sin(15))^2+(cos(15))^2)=(3^0,5)/2)*((sin(15))^2-(cos(15))^2)=-(3^0,5)/2)*cos(30)=-0,75;
ответ. ((3^0,5)/2)*((cos(75))^4-(cos(15))^4)=((3^0,5)/2)*((sin(15))^2-(cos(15))^2)*((sin(15))^2+(cos(15))^2)=(3^0,5)/2)*((sin(15))^2-(cos(15))^2)=-(3^0,5)/2)*cos(30)=-0,75;