(y^2+2xy-cos(y+z))/(e^z+cos(y+z))没有过程吗？求导：e^z * dz -y^2-2xy+cos(y+z)(1+dz)=0把含有dz的项移到一起：(e^z+cos(y+z))dz=y^2+2xy-cos(y+z)把dz的系数除到等式右边：dz=(y^2+2xy-cos(y+z))/(e^z+cos(y+z))