Triangle BFG has angles [beta], [phi], and 1/2 [pi] with corresponding opposite edges of angular length b, f and g.
The procedure's input parameters are angles [beta] and [gamma], an angular length PD and an angular length AB.
The procedure's input parameters are angular length d (see Equation (14)) and angle [psi].
The procedure's input parameters are angles [beta], [gamma] and [rho], and angular length AB.
In spherical triangle T, point P splits angular length BD into angular length x and angular length y, and in plane triangle T' point P' splits B'D' into length x' and length y' (Figure 17).
To understand these limits, the intersection I of a spherical cap defined by angular length s, and, originating from the center of that cap, an infinitely tight spherical lune defined by two great circles with angle [tau] are constructed (Figure 18a).