## Understanding Triangle Geometry

**Cheat Sheet for 9th Grade Geometry**

Circumcenter | Intersection of lines bisecting the sides |

Incenter | Intersection of lines bisecting the angles |

Altitude | Perpendicular line from a vertex (angle) to the opposite side |

Othocenter | Where the altitudes intersect |

Median | Line from an angle to the midpoint of the opposite side |

Centroid | Intersection of the median lines or (x1+x2+x3)/3 , (y1+y2+y3)/3 |

Distance | sqrt((x2-x1)^{2} + (y2-y1)^{2}) |

Pythagaros | h = sqrt(a^{2} + b^{2}) |

Line | y = mx + b |

Midpoint of a line | (x1+x2)/2 , (y1+y2)/2 |

Slope | (y2-y1)/(x2-x1) memory aid "rise over run" |

Area | base/2 * height |