首页 > 留学知识库

问题: 求导

sin^4(x/4)+cos^4(x/4)
麻烦写个过程,答案-1/4(sinx)

解答:

f'(x)=4sin^3(x/4)cos(x/4x)(1/4)+4cos^3(x/4)(-sin(x/4))(1/4)
=(sin^3(x/4)cos(x/4)-cos^3(x/4)sin(x/4)
=(1/2)[sin^2(x/4)sin(x/2)-cos^2(x/4)sin(x/2)]
=(-1/2)sin(x/2)[cos^2(x/4)-sin^2(x/4)]
=(-1/4)[2sin(x/2)cos(x/2)]
=(-1/4)sinx