 When a particle travels from point P to point Q over formula_6, as it does in the illustration to the left, the radius of the circle goes through a change in angle formula_7 which equals the "angular displacement".In three dimensions, angular displacement is an entity with a direction and a magnitude.The direction specifies the axis of rotation, which always exists by virtue of the Euler's rotation theorem; the magnitude specifies the rotation in radians about that axis (using the right-hand rule to determine direction).