原来函数=lnx
x=y²
y=sinw
w=u²
所以原式=1/x*x'
=1/sin²(u²)*2y*y'
=1/sin²(u²)*2sinu²*cosw*w'
=1/sin²(u²)*2sinu²*cosu²*2u
=2ucosu²/sinu²
=2ucot(u²)