1.已知f(cosX)=cos3X,则f(sinX)等于?

问题描述:

1.已知f(cosX)=cos3X,则f(sinX)等于?
请把过程写完整哈,谢啦.

f(sinx)
=f[cos(π/2-x)]
=cos3(π/2-x)
=cos(3π/2-3x)
=-sin3x