A.k.a. Desargues' Homology Theorem.
[b]Proposition: [/b] For two triangles,
[i]The intersections of the lines through corresponding sides are collinear ≡ The lines through corresponding vertices meet at a point.[/i]
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Desargues Homology Theorem:
1) Pappus' Theorem: [url]http://www.geogebratube.org/material/show/id/35140[/url]
2) Vector notation: [url]http://www.geogebratube.org/material/show/id/35213[/url]
[b]3) Desargues' Theorem[/b]
This is problem #59 in Heinrich Dorrie's [i]100 Great Problems of Elementary Mathematics[/i]
