A treatise of trigonometry, [electronic resource] : plane and spherical, theoretical and practical. In which the several cases of plane and spherical triangles are solved, instrumentally and arithmetically. As likewise a Treatise of Stereographick and Orthographick Projection of the Sphere. In which the Principles and Theorems on which they depend, are clearly Demonstrated, and the Practice naturally deduced from those Demonstrations. Illustrated in the Stereographick Projection of the several Cases in Right and Oblique Angled, Spherical, Triangles: So that the Requisites may be found without Calculation, by Scale and Compass. The second edition, carefully corrected by the author Sam. Heynes, Teacher of the Mathematicks.