Sin x * sin y = 1/2 (cos (x-y) - cos(x+y))
cos (x-y) - cos(x+y) = sqrt(3)/2
cosx * cosy = 1/2 (cos (x-y) + cos(x+y))
cos (x-y) + cos(x+y) = sqrt(3)/2
2 * cos(x-y) = sqrt(3)
cos(x-y) = sqrt(3)/2
x-y = +- (pi/6) + 2pi * k
справишься дальше?
Ответ в приложении &^//$#$##@@
(7b+b^5)^2=49b^2+14b^6+b^10