First Part of an Elementary Treatise on Spherical Trigonometry

A'BC acute adjacent angles angles are given becomes calculated called Corollary corresponding cosec cosine cotan deduced Demonstration denote determined differs divided equal to 90 equation EXAMPLES expressions factor fall on AC Fourthly fractions given angle gives greater than 90 half the sum hemisphere Hence hypothenuse impossible included angle known leads legs Lemma less than 90 Let ABC fig let fall logarithm lunary surface measured middle negative numerator obtained obtuse opposite angle opposite side perpendicular perpendicular BP positive preceding Problem proportion proved quantity quotient reduce result right angle Rules satisfy Scholium second member Secondly sides and angles sides equal signs sine Solution solve a spherical solve the triangle spherical right triangle spherical triangle ABC substituted supplements surface ABC tang tangent of half Theorem Thirdly tive trian triangle ABC figs whence