dydx的精选

令t=x+yy=t-xdy=d(t-x)d(t-x)/dx=t^2dt/dx-1=t^2dt/dx=t^2+1dt/(t^2+1)=dxarctant=x+carctan(x+y)=x+c所以正确答案应该是：arctan(x+y)=x+c...