## dihedral angleThe angle defined by two planes or two faces of a polyhedron meeting at an edge; for example, all the dihedral angles of a cube are 90°. An almost-spherical polyhedron (with many faces) has small dihedral angles. A dihedral angle is described by a point on one of the planes or faces, the line of intersection (edge), and a point on the other plane. Should a point P on one of the planes be so positioned that the line through
it perpendicular to the edge E,
intersects E at the same point as a line drawn perpendicular to
E through a point P' on the other plane, then the angle
PEP' is the plane angle of the dihedral angle.
All plane angles of a dihedral angle are equal. ## Related category• SOLIDS AND SURFACES | |||||

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