THEOREM OF THE DAY: Pappus’ Theorem

Theorem

Let $A, B, C$ and $a, b, c$ be two sets of collinear points. Let $A$ be joined by a line to $b$ and $c$; $B$ to $a$ and $c$; and $C$ to $a$ and $b$. Then the intersection points of the line pairs $Ab$ with $Ba$, $Ac$ with $Ca$ and $Bc$ with $Cb$ are again collinear.

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