T

-

the name of the triangle

A, B, C

-

three points

l1, l2, l3

-

three lines

n

-

(optional) list of three names representing the names of the x-axis, y-axis and the z-axis respectively.

form(T)

returns the form of the geometric object (i.e., triangle3d if T is a triangle).

DefinedAs(T)

returns the list of three vertices of T

detail(T)

returns a detailed description of the triangle T.