преобразуйте в произведение:

6.25
1) sin(11п/12) + sin(11п/12) = 2sin((11п/12+5п/12)/2)cos((11п/12-5п/12)/2) = 2sin(2п/3)cos(п/4)
2)cos6a-cos3a=-2sin((6a+3a)/2)sin((6a-3a)/2)=-2sin(4,5a)sin(1,5a)