## Quick Reference

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

Theorem

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.