# dihedral angle

Two distinct half-planes, emanating from a same line $l$, the space ($\mathbb{R}^{3}$) into two regions called .  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 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 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