"Desargues also gives the theory of polar lines. What is called "" in elementary works is as follows: If the vertices of two triangles, situated either in space or in a plane, lie on three lines meeting in a point, then their sides meet in three points lying on a line, and conversely. This theorem has been used since by Brianchon, Sturm, Gergonne, and others. Poncelet made it the basis of his beautiful theory of homological figures."
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Florian Cajori, A History of Elementary Mathematics: with Hints on Methods of Teaching (1897)
https://en.wikiquote.org/wiki/Girard_Desargues
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Girard Desargues
(21 February 1591 – September 1661) was a French mathematician, architect and engineer, who is considered one of the founders of . , the , and the Desargues crater are named in his honour.
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