An altitude from the vertex A of a triangle ABC is a line segment (or its extension) from vertex A perpendicular to the side BC.

If the optional argument H is given, the object returned (hA) is a line segment AH where H is the projection of A onto the side BC. If it is not given, the object returned is a line passing through A and is perpendicular to the side BC.

For a detailed description of the altitude hA, use the routine detail (i.e., detail(hA);)

The command with(geom3d,altitude) allows the use of the abbreviated form of this command.

Warning, assume that the parameter in the parametric equations is _t
Warning, assuming that the names of the axes are _x, _y, and _z