2cos(x+y)cosx-cos(2x+y)化简
问题描述:
2cos(x+y)cosx-cos(2x+y)化简
答
2cos(x+y)cosx-cos(2x+y)
=2cos(x+y)cosx-cos[(x+y)+x]
=2cos(x+y)cosx-cos(x+y)cosx+sin(x+y)sinx
=cos(x+y)cosx+sin(x+y)sinx
=cos[(x+y)-x]
=cosy