Desargues' theorem on perspective triangles
Triangles and are said to be in perspective if the joins of corresponding points are concurrent.
[i.e. The lines meet at a point.]
For such triangles the meets of corresponding sides are collinear.
[i.e. lie on a straight line.]
This can be summarised as:
Triangles which are in perspective from a point are in perspective from a line.
Last Updated August 2020