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 33
nd thereupon taking away the triangles equal to them DCB and HFG. Therefore |> (S—jt) is the size of the quadrilateral ABCD and at thesame time also that of the spherical triangle in which the sum of thethree angles is equal to S. 28 THEORY OF PARALLELS. 28. If three planes cut each other in… … Fig. 20.points A, B, C, and suppose through these a plane passed, which con-sequently -will cut the planes of the parallels along the straight linesAB, AC, and BO. Further, pass through the line AC and any pointD on the BB, another plane, whose intersection with the two planes ofthe parallels AA…
Geometry, Non-Euclidean
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