Two triangles are said to be perspective if the lines connecting their vertices are concurrent, that is, meet at a point. That point of concurrency is called the perspector.
The term originates from projective geometry, itself an outgrowth of the concept of perspective, the trick used by artists to give the illusion of depth on a two dimensional painting. The etchings of Albrecht Dürer (1471-1528) shows the early Renaissance artist's take on the matter: 1, 2, 3.
Internet References
- Paul Yiu, "A Tour of Triangle Geometry"
- Alexander Bogomolny, Pole and Polar with Respect to a Triangle, from his "Cut the Knot," web site. Wonderful use of Java applet to let you move around an interior point P and see how the perspector affects things such as lines of concurrency.