quadrantal versor  From The Collaborative International
Dictionary of English v.0.48:  Quadrantal \Quad*ran"tal\, a. [L.
quadrantalis containing the    fourth fourth part of a measure.]
(Geom.)    Of or pertaining to a quadrant; also, included in the
fourth    part of a circle; as, quadrantal space.    [1913
Webster]     Quadrantal triangle, a spherical triangle having
one side       equal to a quadrant or arc of 90[deg].
Quadrantal versor, a versor that expresses rotation through
one right angle.       [1913 Webster]  From The Collaborative
International Dictionary of English v.0.48:  Versor \Ver"sor\,
n. [NL., fr. L. vertere, versus, to turn. See    Version.]
(Geom.)    The turning factor of a quaternion.    [1913 Webster]
Note: The change of one vector into another is considered in
quaternions as made up of two operations; 1st, the
rotation of the first vector so that it shall be
parallel to the second; 2d, the change of length so
that the first vector shal