# Menelaus' theorem ( transversal line passes inside triangle )

## Description

Menelaus’ theorem, named for Menelaus of Alexandria, is a theorem about triangles in plane geometry. Given a triangle ABC, and a transversal line that crosses BC, AC and AB at points D, E and F respectively, with D, E, and F distinct from A, B and C, then there is a relation between the segments.The equation uses signed lengths of segments, in other words the length AB is taken to be positive or negative according to whether A is to the left or right of B in some fixed orientation of the line. For example, AF/FB is defined as having positive value when F is between A and B and negative otherwise.

Related formulas## Variables

AF | Segment on AB side of the triangle (dimensionless) |

FB | Other Segment on AB side of the triangle (dimensionless) |

BD | Segment on BC side of the triangle (dimensionless) |

DC | Other Segment on BC side of the triangle (dimensionless) |

CE | Segment on AC side of the triangle (dimensionless) |

EA | Other Segment on AC side of the triangle (dimensionless) |