Library/Geometry/Solid geometry/Lines and planes in space/Dihedral angle

Dihedral angle

Overview
Important

A dihedral angle is the angle formed between two planes that meet along a common line (called the edge or intersection line). To measure the dihedral angle, you can pick any point on the intersection line, draw one line in each plane perpendicular to the intersection line at that point, and then measure the angle between these two lines. This angle is the dihedral angle.

Important properties

  • The dihedral angle is always measured between 0° and 180°.

  • The size of the dihedral angle does not depend on which point you choose along the intersection line.

  • If the two planes are perpendicular, the dihedral angle is 90°.

  • If the two planes are parallel, the dihedral angle is 0° (or 180°).