Решение:
1) sina*sinb-cos(a-b)=sina*sinb-cosa*cosb-sinasinb=-cosa*cosb
-cosa*cosb:ctga=-cosa*cosb*sina/cosa=-cosb*sina
2) cos2x-1=-2sin^2x ( Второе условие под вопросом)
(a²-9b²)/(0,5a+1,5b)=(a²-(3b)²)/(0,5a+1,5b)=2*(a2-(3b)²)/(2*(0,5a+1,5b))=
=2*(a+3b)(a-3b)/(a+3b)=2*(a-3b)=2a-6b=1.
<span>Кхм.........</span>
<span>C =150 +11*(16-5)=271</span>