Questions on hyperbolic geometry, the geometry on manifolds with negative curvature.

The prototypical example of hyperbolic geometry in two dimensions is Gauss-Lobachevsky-Bolyai geometry, in which the parallel postulate of Euclidean geometry is replaced by the postulate of there being at least 2 parallel lines through a given point to a given line, and the sum of interior angles for a triangle being smaller than $\pi$ radians.

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