cos(b-a)
=cos(a-b)
cos是偶函数,cos(-x)=cosx
sin(a-b)cosb+cos(b-a)sinb
=sin(a-b)cosb+cos(a-b)sinb
=sin(a-b+b)
=sina
请及时点击右下角的【好评】按钮
cos(b-a)
=cos(a-b)
cos是偶函数,cos(-x)=cosx
sin(a-b)cosb+cos(b-a)sinb
=sin(a-b)cosb+cos(a-b)sinb
=sin(a-b+b)
=sina
请及时点击右下角的【好评】按钮