Plotting a set of R^2 using three variables

edit

Some workaround:

E = EuclideanSpace(3)
cylindrical.<rh,ph,z> = E.cylindrical_coordinates()
cartesian.<x,y,z> = E.cartesian_coordinates()
p=cylindrical.plot(cartesian,ranges={rh:(1,2),ph:(0,pi/4),z:(0,3)},
    number_values={rh:2,ph:15,z:2},thickness=2,
    color={rh:'red', ph:'green',z:'blue'},label_axes=False)
p.show(frame=False)

For the subset of $\mathbb{R}^2$, use the function region_plot:

x, y = var('x y')
region_plot([0<=x, x<=y, 1<=x^2+y^2, x^2+y^2<= 4], (x, -2, 2), (y, -2, 2))

For more details, see the description of region_plotat the end of the page https://doc.sagemath.org/html/en/refe...

For a subset of $\mathbb{R}^3$, unfortunately there does not seem to be any function equivalent to region_plot in Sage...