Geometrical researches on the theory of parallels (1914)
Lobachevskiĭ, N. I. (Nikolaĭ Ivanovich), 1792-1856, Halsted, George Bruce, 1853-1922, Lobachevskiĭ, N. I. (Nikolaĭ Ivanovich), 1792-1856. Geometrische Untersuchungen zur Theorie der Parallellinien English · Chicago [etc.] Open Court Publishing Company · leaf 18
ntersection of a sphere with a plane is a circle. 13. A straight line at right angles to the intersection of two per-pendicular planes, and in one, is perpendicular to the other. 14. In a spherical triangle equal sides he opposite equal angles, andinversely. 15. Spherical triangles are congruent… … 16. All straight lines which in a plane go out from a point can,with reference to a given straight line in the same plane, be dividedinto two classes—into cutting and not-cutting. The boundary lines of the one and the other class of those lines willbe called parallel to the given line. <j From…
Geometry, Non-Euclidean
Internet Archive · Cornell University Library · Public Domain Mark 1.0. Free to use for anything.
