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Once a mainstay of mathematics, spherical trigonometry no longer appears on school curricula.

The calculation of the angles between the normals of faces and between zone-circles is then performed by the ordinary methods of spherical trigonometry.

The formula is Probably nearly contemporary with Heron was Menelaus of Alexandria, who wrote a spherical trigonometry.

These formulae are the foundation of spherical trigonometry.

When I left Woolwich my coarse in mathematics consisted of plane and spherical trigonometry, conic sections, statics and dynamics, properties of roofs and arches, hydrostatics, projectiles, and the deferential and integral calculus.