Spherical trigonometry

ambiguity angular approximately arcs base calculated called centre circle circular considered constant corresponding cos a cos cos³ cosines deduce demonstrated denote described determine draw drawn edges elements equal equation error example expressed faces figure fixed points formed formula formulæ four give given greater Hence inscribed known length less measured meet method middle point Napier's observed obtain opposite sides perpendicular plane polar triangle pole polygon position preceding Article produced quadrant radius regular polyhedron relation remain respectively result right angles right-angled triangles Rules shew shewn sides Similarly sin b sin sin³ sine small circle solid angles solution sphere spherical excess spherical triangle straight lines supplement suppose surface tetrahedron theorem third touches triangle ABC