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Close to Unity Fraction

  1. Feb 2, 2009 #1
    If you have a fraction, for example,
    [tex]\frac{1}{{1.0091532\times10^{-12}} + 1}[/tex]

    Is there a simple way to convert it to a more easily calculated form, specifically, 1-x (where x is a very small number)
     
  2. jcsd
  3. Feb 2, 2009 #2

    CRGreathouse

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    1/(1+a) = 1 - a/(1 + a), which for tiny a is about 1 - a. More precisely,
    1/(1+a) = 1 - a/(1 + a) = 1 - a + a^2/(1 + a)
    which is about 1 - a + a^2 for tiny a.
     
  4. Feb 2, 2009 #3

    symbolipoint

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    Just arrange an equation based on that.
    1 - x = [tex]\frac{1}{{1.0091532\times10^{-12}} + 1}[/tex]

    Determine an expression for the value of x, and then rewrite the left-hand expression.
     
  5. Feb 2, 2009 #4
    Expanding on what CRGreathouse says, the Taylor series (around 0) for 1/(1 + x) is 1 - x + x2 - x3 + ... (and it converges if |x| < 1). You can approximate it by truncating the Taylor series, and since you have x ~ 10-12, for practical purposes 1 - x should be enough (any higher-order terms will be smaller than the precision you give anyway).
     
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