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What does |x| mean in the erf function?

  1. Sep 11, 2010 #1
    Here's the equation I'm using: erf(x) = x/|x| * SQRT(1 - exp(-x2*(4/pi + (ax)2) / (1 + ax2)
  2. jcsd
  3. Sep 11, 2010 #2
    |x| is the absolute value of x.

    x/|x| is 1 for positive x, -1 for negative x.

    (However, I don't recognize that equation for erf.)
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