求dy/dx=(x/y)+cos²(x/y)通解令x/y=u,则y=x/u,dy/dx=[u-x(du/dx)]/u²,代入原式得：[u-x(du/dx)]/u²=u+cos²u=u+(1+cos2u)/2u-x(du/dx)=u³+u²(1+cos2u)/2u³-u+u²(1+cos2u)/2=...