Ellipsoid:

> implicitplot3d( x^2/4 + y^2/9 + z^2 = 1, x=-2..2, y=-3..3, z=-1..1, grid=[9,9,9], scaling=constrained, axes=boxed );

>

> plot3d( [ 2*cos(t)*cos(s), 3*sin(t)*cos(s), sin(s) ], t=0..2*Pi, s=0..2*Pi, scaling=constrained, axes=boxed );

>