设y=ln[cos(1+3x^2)],则dy=
问题描述：
设y=ln[cos(1+3x^2)],则dy=
答
dy=6x*[-sin(1+3x²)]dx/[cos(1+3x²)]
=-6xsin(1+3x²)dx/[cos(1+3x²)]后面要加dx