Finding the orthocenter of a triangle in the plane

The orthocenter command finds the orthocenter of a triangle.

orthocenter takes T, a triangle. The triange can also be specified with three points.
orthocenter(T) returns the orthocenter of T.

triangle(-i/2,1+i,-1+i), orthocenter(triangle(-i/2,1+i,-1+i))

or:

triangle(-i/2,1+i,-1+i), orthocenter(-i/2,1+i,-1+i)

which is the point (0,0), the orthocenter of the triangle.