"By spherical trigonometry, certainly," said Mendelssohn pleasantly.
spherical trigonometry: solution of triangles, and application to nautical astronomy.
Probably nearly contemporary with Heron was Menelaus of Alexandria, who wrote a spherical trigonometry.
He lived c. 1085, at Seville, and wrote on astronomy and spherical trigonometry.
For calculating arcs in astronomy from other arcs given by means of tables he used propositions in spherical trigonometry.
Musa, above mentioned, was the author of a "Treatise on spherical trigonometry."
As early as 1000 spherical trigonometry was in use, and Aboul-Hassan wrote an excellent treatise on conic sections.
He invented the sciences of plane and spherical trigonometry, and was the first to use right ascensions and declinations.
By this time I had studied plane and spherical trigonometry, conic sections, and Fergusson's "Astronomy."