2sin(x+y)*siny+cos(x+2y)可以化简为什么?请尽快回答

分类: 作业答案 • 2022-07-28 21:46:37

问题描述：

2sin(x+y)*siny+cos(x+2y)可以化简为什么?
请尽快回答

答

=2sin(x+y)siny+cos(x+y+y)
=2sin(x+y)siny+cos(x+y)cosy-sin(x+y)siny
=sin(x+y)siny+cos(x+y)cosy
=cos(x+y-y)
=cosx

答

2sin(x+y)*siny+cos(x+2y)
=2sin(x+y)*siny+cos[(x+y)+y]
=2sin(x+y)siny+cos(x+y)cosy-sin(x+y)siny
=cos(x+y)cosy+sin(x+y)siny
=cos[(x+y)-y]
=cosx