Clear[f]; f[x y ]=2x 2+y 2 plPlot3D(fx,]x,-2, 2,,-2, 2) gl=ParametricPlot3D[rSin[u/Sqrt[2. r*Cos[u] r 2),u,0, 2Pi, r, 0,2)1 a=D[fxy]x].{x->1y->1} b=Dfx, yly].x->l,y->1 f1,1]+a(x-1)+b(y-1) 2=Plot3D[pxy]{x,-2,2},{y-2,2 ly[x =1+b(x-1)/a Iz[x =f[l, 1]-(x-1)a; g3=-ParametricPlot3DRX, lyx],Iz[x,(x-2, 2] Showlpl, g2, g3, AspectRatio->Automatic, ViewPoint->(-2.530,-1.025, 2.000] 结果Clear[f];f[x_,y_]=2x^2+y^2; p1=Plot3D[f[x,y],{x,-2,2},{y,-2,2}]; g1=ParametricPlot3D[{r*Sin[u]/Sqrt[2.],r*Cos[u],r^2},{u,0,2*Pi},{r,0,2}]; a=D[f[x,y],x]/.{x->1,y->1}; b=D[f[x,y],y]/.{x->1,y->1}; p[x_,y_]=f[1,1]+a(x-1)+b(y-1); g2=Plot3D[p[x,y],{x,-2,2},{y,-2,2}]; ly[x_]=1+b(x-1)/a;lz[x_]=f[1,1]-(x-1)/a; g3=ParametricPlot3D[{x,ly[x],lz[x]},{x,-2,2}]; Show[p1,g2,g3,AspectRatio->Automatic,ViewPoint->{-2.530,-1.025,2.000}]; 结果：