Hi:

Here are a few examples which I think are interesting.

If anyone can figure out a way to plot a cardioid,
http://mathworld.wolfram.com/HeartSurface.html,
in SAGE, I'd be very interested.

- David Joyner

#M\"obius strip:
sage: u,v = var("u,v")
sage: p = parametric_plot3d([cos(u)*(1+v*cos(u/2)),
sin(u)*(1+v*cos(u/2)), 0.2*v*sin(u/2)], (u,0, 4*pi), (v,0,
0.3),plot_points=[50,50])

#twisted ribbon
sage: p = parametric_plot3d([3*sin(u)*cos(v), 3*sin(u)*sin(v),
cos(v)], (u,0, 2*pi), (v, 0, pi),plot_points=[50,50])

#ellipsoid (automatically rescaled axes make it look spherical)
sage: p = parametric_plot3d([3*sin(u)*cos(v), 2*sin(u)*sin(v),
cos(u)], (u,0, 2*pi), (v, 0, 2*pi),plot_points=[50,50])

#cone
sage: p = parametric_plot3d([u*cos(v), u*sin(v), u], (u, -1, 1), (v,
0, 2*pi), plot_points=[50,50])

#paraboloid
sage: p = parametric_plot3d([u*cos(v), u*sin(v), u^2], (u, 0, 1), (v,
0, 2*pi), plot_points=[50,50])

#hyperboloid
sage: p = plot3d(u^2-v^2, (u, -1, 1), (v, -1, 1), plot_points=[50,50])

#weird looking surface - like a M\"obius band but also an O
sage: p = parametric_plot3d([sin(u)*cos(u)*log(u^2)*sin(v),
(u^2)^(1/6)*(cos(u)^2)^(1/4)*cos(v), sin(v)], (u, -1, 1), (v, -pi,
pi), plot_points=[50,50])


#a heart, but not a cardioid (for my wife)
sage: p1 = parametric_plot3d([sin(u)*cos(u)*log(u^2)*v*(1-v)/2,
((u^6)^(1/20)*(cos(u)^2)^(1/4)-1/2)*v*(1-v), v^(0.5)], (u, 0.001, 1),
(v, 0, 1), plot_points=[90,90])
sage: p2 = parametric_plot3d([-sin(u)*cos(u)*log(u^2)*v*(1-v)/2,
((u^6)^(1/20)*(cos(u)^2)^(1/4)-1/2)*v*(1-v), v^(0.5)], (u, 0.001, 1),
(v, 0, 1), plot_points=[90,90])
sage: show(p1+p2, frame=False)

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