If a point in the Hilbert cube is specified by a sequence \ lbrace a _ n \ rbrace with 0 \ leq a _ n \ leq 1 / n, then a homeomorphism to the infinite dimensional unit cube is given by h ( a ) _ n = n \ cdot a _ n.
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In geometry, the "'Beltrami Klein model "', also called the "'projective model "', "'Klein disk model "', and the "'Cayley Klein model "', is a model of hyperbolic geometry in which points are represented by the points in the interior of the unit disk ( or " n "-dimensional unit ball ) and lines are represented by the ideal endpoints on the boundary sphere.
