先对ln求导,得1/sin(1+3x^2)
然后对真数,即sin(1+3x^2)求导,是cos(1+3x^2)
然后对1+3x^2求导,是6x
最后相乘
y'=6xcos(1+3x^2)/sin(1+3x^2)
即y'=6xcot(1+3x^2)