First of all, P is in itself a graphics object. Writing plot3d(P) does not make much sense.
Secondly, f is a one-variable function so that plot(f) is a 2 dimensional picture (that works). But then the addition plot(f)+plot3d(P) is trying to concatenate a 2-dimensional and a 3-dimensional picture that looks weird.
Now, to draw a curve in 3d you can for example use parametric_plot3d.
To get your plot using the parametric_plot3d command that vdelecroix suggested, you could try:
u = var('u')
parametric_plot3d([2,u,u^2],(u,-2,2))
The result, running in a SageCellServer is shown:
Note that the command var('u') defines u: you should be able to use var('u') rather than u = var('u'). Unfortunately many of the examples in the Sage documentation needlessly use the longer version.
Asked: 2020-02-04 23:19:29 +0100
Seen: 906 times
Last updated: Feb 05 '20
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You can use
var('y')to defineyas a variable, and similarly forz.