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