Math 2.0

concept

Cross-ratio

Summary

The cross-ratio is a number made from four points of a line, or of the Riemann sphere, see the definition. It does not change under Möbius transformations and, more generally, under projective transformations.

What this node needs for W2
  • edge instance_of in: at least two examples (0 of 2)
  • edge not_instance_of in: at least one non-example (0 of 1)
  • edge specializes both: the more general notions and the special cases (0 of 1)

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Sources

  1. Web https://en.wikipedia.org/wiki/Cross-ratio, lead section

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Definitions