Dihedral Angle

Dihedral Angle

In geometry, a dihedral or torsion angle is the angle between two planes.

The dihedral angle of two planes can be seen by looking at the planes "edge on", i.e., along their line of intersection. The dihedral angle between two planes denoted A and B is the angle between their two normal unit vectors and

A dihedral angle can be signed; for example, the dihedral angle can be defined as the angle through which plane A must be rotated (about their common line of intersection) to align it with plane B. Thus, . For precision, one should specify the angle or its supplement, since both rotations will cause the planes to coincide.

In higher dimension, a dihedral angle represents the angle between two hyperplanes.