# dihedral angle

Two distinct half-planes, emanating from a same line $l$, the space (${\mathbb{R}}^{3}$) into two regions called dihedral angles^{}. The line $l$ is the edge of the dihedral angle and the bounding half-planes are its sides.

The angle, which the sides of a dihedral planes separate from a normal plane^{} of the edge, is the normal section^{} of the dihedral angle. Apparently, all normal sections are equal. According to the of the normal section, the dihedral angle may be called acute, right, obtuse, straight, skew (http://planetmath.org/ConvexAngle), convex and concave. Unlike the angle between two planes, a dihedral angle may be over 90 .

If two planes intersect each other and if one of the four dihedral angles formed is right, then also the others are right. Then we say that the planes are perpendicular^{} to each other.

Title | dihedral angle |

Canonical name | DihedralAngle |

Date of creation | 2013-03-22 18:48:07 |

Last modified on | 2013-03-22 18:48:07 |

Owner | pahio (2872) |

Last modified by | pahio (2872) |

Numerical id | 9 |

Author | pahio (2872) |

Entry type | Definition |

Classification | msc 51M04 |

Related topic | NormalSection |

Related topic | PerpendicularityInEuclideanPlane |

Related topic | TrihedralAngle |

Related topic | SolidAngle |

Defines | edge |

Defines | side |

Defines | normal section |

Defines | concave |

Defines | perpendicular |

Defines | perpendicular planes |