是不是这个
(sin^A+sin^B)sin(A-B)=(sin^A-sin^B)sin(A+B)
sin^A*(sin(A+B)-sin(A-B))=sin^B*(sin(A-B)+sin(A+B))
乘出来
sin^A*sin(A-B)+sin^B*sin(A-B)=sin^A*sin(A+B)-sin^B*sin(A+B)
移项
sin^A*sin(A+B)-sin^A*sin(A-B)=sin^B*sin(A-B)+sin^B*sin(A+B)
所以sin^A*(sin(A+B)-sin(A-B))=sin^B*(sin(A-B)+sin(A+B))