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I Section formula, external ratio

  1. May 11, 2016 #1
    I want to know how mathematician got the idea of external division , how they can say that a point can divide a line externally, what's the reason behind this discovery . Why they discovered it.
  2. jcsd
  3. May 11, 2016 #2


    Staff: Mentor

  4. May 12, 2016 #3


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    2017 Award

    Staff: Mentor

    I assume because of the invariance of the ratios under affine mappings, e.g. parallel projections. These mappings are essential to the constructions @jedishrfu mentioned.
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