Spherical_Quadrilateral_Beta_Angle_Aerospace_and_Robotics_Rotation_Matrices

My spherical quadrilateral. I created that in 1990 or so from four great circles. The spherical triangle (formed from three great circles on a sphere) is well known in an ancient (up to 1945, I suppose) discipline called spherical trigonometry. I see two spherical triangles in my figure.

Done