Ceva's Theorem

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The following theorem, due to Giovanni Ceva (1648–1734) and published in 1678:


Let L, M and N be points on the sides BC, CA and AB of a triangle (possibly extended). Then AL, BM and CN are concurrent if and only if(Note that BC, for example, is considered to be directed from B to C so that LC, for example, is positive if LC is in the same direction as BC and negative if it is in the opposite direction; see measure). See Menelaus' Theorem.

Subjects: Mathematics.

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