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Math Help - What I dont understand is

  1. #1
    MHF Contributor Mathstud28's Avatar
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    What I dont understand is

    After deriving "erf(x)" with Maclaurin series...I am still oblivous as to two things...where to 2/pi^(1/2) came from and as to say if I was integrating e^(-x) from 4 to 2 how I would plug in numbers into erf(x) to acheive the numerical answer? Could someone help?
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  2. #2
    Flow Master
    mr fantastic's Avatar
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    Quote Originally Posted by Mathstud28 View Post
    After deriving "erf(x)" with Maclaurin series...I am still oblivous as to two things...where to 2/pi^(1/2) came from and as to say if I was integrating e^(-x) from 4 to 2 how I would plug in numbers into erf(x) to acheive the numerical answer? Could someone help?
    2/pi^(1/2) is a constant that is introduced so that erf(+oo) = 1. There are good reasons for doing this.

    \int_a^b e^{-x^2}\, dx = \frac{\sqrt{\pi}}{2} (\text{erf} (b) - \text{erf} (a)).
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  3. #3
    MHF Contributor Mathstud28's Avatar
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    Hmm

    That is what I thought obviously since F(b)-F(a) where F'(x)=f(x) but I swore I did it and got the wrong values...
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