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Shortcut for Quotient Rule

  1. Dec 9, 2012 #1
    Hi Guys,
    I remember back in the days of Calc I learning that there was an easy way to take multiple derivatives of certain functions that needed repeated uses of the quotient rule. I was wondering if anybody remembered that trick.
     
  2. jcsd
  3. Dec 9, 2012 #2

    jedishrfu

    Staff: Mentor

    is this like using the difference of squares to reduce the function into a product of factors that you then can use the product or quotient rule on:

    http://calculustricks.com/page/3/
     
  4. Dec 10, 2012 #3
    It involved the denominator and easily reducing something in the numerator instead of having to do all the distributing and addition to then reduce. Instead of squaring the denominator everytime you only increased it's power by one. Also it has a factorial pattern in there if i recall correctly.
    Like here:

    http://www.wolframalpha.com/input/?i=derivative+arctan(x)&lk=4&num=1
    http://www.wolframalpha.com/input/?i=+2nd+derivative+arctan(x)
    http://www.wolframalpha.com/input/?i=+3rd+derivative+arctan(x)
    http://www.wolframalpha.com/input/?i=4th+derivative+arctan(x)
    http://www.wolframalpha.com/input/?i=5th+derivative+arctan(x)

    and another function
    http://www.wolframalpha.com/input/?i=derivative+1/(x+1)
    http://www.wolframalpha.com/input/?i=2nd+derivative+1/(x+1)
    http://www.wolframalpha.com/input/?i=3rd+derivative+1/(x+1)
    http://www.wolframalpha.com/input/?i=3rd+derivative+x%2F%28x^3%2B1%29
     
  5. Dec 10, 2012 #4

    jedishrfu

    Staff: Mentor

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