var('x,y') f(x,y) = y^3 -x^3 -1 G = f.gradient() G(x,y)
Champ = plot_vector_field([y^2,x^2],(x,-2,2),(y,-2,2), color="blue") Courbe = implicit_plot(f(x,y) == 0 , (x,-2,2), (y,-2,2), color= "red") show(Champ + Courbe)
var('s,t') def x(t) : return 10*cos(t) def y(t) : return 10*sin(t) def z(x,y) : return 4+(x^2-y^2)/100 S = parametric_plot3d([x(t),y(t), s*z(x(t),y(t))],(t,0,2*pi),(s,0,1), color= "darkgreen", opacity = 0.35) C = parametric_plot3d([x(t),y(t), z(x(t),y(t))],(t,0,2*pi), color= "red", thickness= 2) show(S+C, frame_aspect_ratio = [1,1,3])