in a projective plane, two triangles<span> are said to </span>be perspective<span> from a </span>point if<span> the three lines</span> joining corresponding<span> vertices of the </span>triangles<span> meet at a common </span>point<span> called the center. ... Desargues' Theorem: </span>If two triangles<span> are </span>perspective<span> from a </span>point then<span> they are </span>perspective<span> from a line.</span>
