Projective geometry (Table of contents)
## Desargue's Theorem

**Theorem 3 (Desargue's theorem)**
Two triangles are perspective with respect to a center if
and only if they are perspective with respect to a point.

The triangles \(A_1B_1C_1\) and \(A_2B_2C_2\) are
*perspective with respect to a center*
if the lines \(A_1A_2\), \(B_1B_2\), and \(C_1C_2\)
are concurrent. They are *perspective with respect to
an axis*
if the points \(K=B_1C_1\cap B_2C_2\),
\(L=A_1C_1\cap A_2C_2\), \(M=A_1B_1\cap A_2B_2\) are colinear.