 Two triangles "ABC" and "abc" are said to be in perspective centrally if the lines "Aa", "Bb", and "Cc" meet in a common point, called the "center of perspectivity".They are in perspective axially if the intersection points of the corresponding triangle sides, , , and all lie on a common line, the "axis of perspectivity".Desargues' theorem in geometry states that these two conditions are equivalent