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| − | {{stub}}
| + | #REDIRECT[[Menelaus' theorem]] |
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| − | '''Menelaus' Theorem''' deals with the [[collinearity]] of points on each of the three sides (extended when necessary) of a [[triangle]].
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| − | It is named for Menelaus of Alexandria.
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| − | == Statement ==
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| − | A necessary and sufficient condition for points <math>D, E, F</math> on the respective side lines <math>BC, CA, AB</math> of a triangle <math>ABC</math> to be collinear is that
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| − | <center><math>BD\cdot CE\cdot AF = -DC\cdot EA\cdot FB</math></center>
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| − | where all segments in the formula are [[directed segment]]s.
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| − | [[Image:Menelaus1.PNG|center]]
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| − | == See also ==
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| − | * [[Ceva's Theorem]]
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| − | * [[Stewart's Theorem]]
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| − | [[Category:Theorems]]
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| − | [[Category:Geometry]]
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