cosxsin(x-1)-sinxcos(x-1)等于多少?

题目

cosxsin(x-1)-sinxcos(x-1)等于多少?

答案

cosxsin(x-1)-sinxcos(x-1)
=sin[(x-1)-x]
=sin(-1)
=-sin1
若看不明白可以这样：
设x-1=y,即y-x=-1
原式=cosxsiny-sinxcosy
=sin(y-x)
=sin(-1)
=-sin1