x, y, z = var("x y z")
S = plot3d(x^2+y^2, (x, -2, 2), (y, -2, 2))
show(S, aspect_ratio=1)
x, y, z = var("x y z")
S = plot3d(x^2+y^2, (x, -2, 2), (y, -2, 2))
R = parametric_plot3d((1, y, z), (y, -2, 2), (z, -1, 8), color="red", opacity=0.5)
show(S+R, aspect_ratio=1)
x, y, z = var("x y z")
S = plot3d(x^2+y^2, (x, -2, 2), (y, -2, 2))
R = parametric_plot3d((x, y, 2), (x, -2, 2), (y, -2, 2), color="red", opacity=0.5)
show(S+R, aspect_ratio=1)