象限球面三角形

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.

{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.