3D scaling | 3D Scaling with Homogeneous Coordinates |

3D solids | General Rules for 3D Solids |

3D translation | 3D Translation with Homogeneous Coordinates |

abscissa | Three-dimensional Cartesian Coordinate System |

| Two-dimensional Cartesian Coordinate System |

acute triangle | Triangle - General Definitions |

altitude | Properties of a Right Triangle |

| Altitudes of a Triangle |

angle | Half Angle Relations in a Triangle |

| Relations between Angles and Sides in Triangles |

| Relations between Angles in Triangles |

angle bisector | Incircle and Angle Bisectors of a Triangle |

angles | Properties of Arbitrary Triangles |

angles of a triangle | Triangle - General Definitions |

ankathete | Properties of a Right Triangle |

annulus | Annulus (Circle Ring) |

antipode | Sphere |

applicate | Cylindrical Coordinate System |

| Three-dimensional Cartesian Coordinate System |

arbitrary triangles | Properties of Arbitrary Triangles |

area | Properties of a Right Triangle |

| Area of a Triangle |

| Ellipse |

| Annulus (Circle Ring) |

| Regular Polygon |

azimuthal coordinate | Cylindrical Coordinate System |