Morph quadrilateral into a triangle

I just purchased Animate 2. For the life of me, I can’t figure out how to morph a rectangle into a trapezoid or triangle. The animate tools act upon the whole element and do not admit to deforming any particular section.

It’s a real puzzler.

Hmmm…, as far as I know, a “Trapezoid” is a 4-sided flat shape with straight sides…
http://www.mathopenref.com/trapezoid.html

A “Quadrilateral” could be any 4-sided shape…
http://www.mathopenref.com/quadrilateral.html

Anyway, morphing a “Square” into a “Triangle”:
(File has been removed)

Thanks, Nolan!

I must admit that, having been an AutoCAD technician for several years at a precast company, I knew the difference of the figures mentioned.

But I really appreciate your quick response.

Thanks again.