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Equivalence relations problem #2 (alg)

  1. Jan 24, 2006 #1
    R = the real numbers

    A = R x R; [tex] (x,y) \equiv (x_1,y_1) [/tex] means that
    [tex] x^2 + y^2 = x_1^2 + y_1^2; [/tex] B= {x is in R | x>= 0 }

    Find a well defined bijection sigma : [tex] A_\equiv -> B [/tex]

    like the last problem, I just cant seem to find the right way to solve this??
  2. jcsd
  3. Jan 24, 2006 #2

    matt grime

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    hint 1 x^2+y^2 is a positive real number.

    hint 2 What is an equivalence class under this relation, think geometrically.

    hint 3 radius.
  4. Jan 26, 2006 #3
    did you get it?
  5. Jan 26, 2006 #4
    ya i did thanks fourier
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