parallelogram(Point1, Point2, Point3)
Draws a parallelogram given three of its vertices. The fourth point is calculated automatically but is not defined symbolically. As with most of the other polygon commands, you can store the fourth point’s coordinates into a CAS variable. The orientation of the parallelogram is counterclockwise from the first point.
parallelogram(0,6,9+5i) draws a parallelogram whose vertices are at (0, 0), (6, 0), (9, 5), and (3,5). The coordinates of the last point are calculated automatically.
parallelogram — Discussion