The great circle distance from LAT 25°50'N, LONG 77°00'W to LAT 35°56'N, LONG 06°15'W is 3616 miles, and the initial course is 061.7°T. Determine the longitude of the vertex, given the latitude of the vertex as 37°34.9'N.

Correct Answer: Option B — 25°59.0'W

The longitude of the vertex is determined by the initial course and the latitude of departure. Using the spherical trigonometry formula sin(DLo) = sin(Initial Course) / cos(Lat_vertex), the difference in longitude from the departure point to the vertex is calculated, resulting in 25°59.0'W.