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![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c8/Desargues_theorem_alt.svg/360px-Desargues_theorem_alt.svg.png)
Credit: Jujutacular
When produced, corresponding sides of two perspective triangles meet at collinear points along the axis of perspectivity. The lines which run through corresponding vertices on the triangles meet at a point called the center of perspectivity. Desargues' theorem guarantees that the truth of the first condition is necessary and sufficient for the truth of the second.
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