444. The great circle distance from LAT 35° 08.0' S, LONG 19° 26.0' E to LAT 33° 16.0' S, LONG 115° 36.0' E is 4559 miles and the initial course is 121° T. Determine the longitude of the vertex.

The vertex longitude is calculated using the great circle vertex formulas, determining the vertex latitude from cos φv = cos φ1 sin C1 and the longitude difference from cos Δλ1v = tan φ1 / tan φv, resulting in 65 45.9' E.