单词	cross ratio
释义	cross ratio For distinct points z1, z2, z3, z4 in the complex plane, their cross ratio equals The definition in the complex plane can be extended to the Riemann sphere by allowing any of the zi to be infinite. The cross ratio in fact can be defined for any distinct four points in a projective line (see projective space), the Riemann sphere here being the complex projective line. See also harmonic range.
随便看	Huygens, Christiaan hydrodynamics hydrostatics Hypatia hyperbola hyperbolic cylinder hyperbolic function hyperbolic geometry hyperbolic paraboloid hyperbolic partial differential equation hyperbolic plane hyperbolic spiral hyperboloid of one sheet hyperboloid of two sheets hypercube hypergeometric distribution hypergeometric series hyperplane hyperreals hypocycloid hypotenuse hypothesis testing Hölder's inequality I I

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