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 29
ORY OF PARALLELS. 26. Triangles standing opposite to one another on the sphere are equiva-lent in surface. By opposite triangles we here understand such as are made on bothsides of the center by the intersections of the sphere with planes; in suchtriangles, therefore, the sides and angles are in… … Fig. 14.at the points A, B, C are likewise equal to those in the other triangle atth pointsA,B,C Through the three points A, B, C, suppose a plane passed, and uponit from the center of the sphere a perpendicular dropped whose pro-longations both ways cut both opposite triangles in the points D and…
Geometry, Non-Euclidean
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