noneuclidian

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    Non-Euclidian Geometry and Cross Ratios

    I am taking a non-euclidian geometry class and it is killing me. I am trying to understand this stuff but it has been many years since I sat in a calculus or geometry class. Here are my problems: 1. If (A,B;C,D) = r, show that (D,C;A,B) = 1/r