Το θεώρημα του Ceva

Given a triangle $ABC$, and points $D, E,$ and $F$ on the sides $BC, CA$, and $AB$ respectively, then the segments $AD, BE$ and $CF$ are concurrent, if and only if 

$\dfrac{FB}{AF} \times \dfrac{DC}{BD} \times  \dfrac{EA}{CE}=1$.

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