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Homework Help: Cot vs arctan

  1. Jul 20, 2012 #1
    I got a answer of

    -11 cot ( 1 / x + 2 )

    the text shews the answer as

    11 arctan ( x + 2 )

    is this the same thing?

    meaning

    -cot(1/x) = arctan(x)?
     
  2. jcsd
  3. Jul 20, 2012 #2
    No, these two are not the same ..
    Also, even if they were, the latter equality you write down wouldn't follow from the former equality because you can't just drop the 2 ..
     
  4. Jul 20, 2012 #3

    uart

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    Science Advisor

    No, cot and arctan are completely different functions JeeebeZ.

    Why don't you post your working. It looks like you may be confusing inverse functions with reciprocals, which is very wrong, but not all that an uncommon mistake for students who are just starting out with manipulating functions.
     
  5. Jul 20, 2012 #4

    uart

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    Science Advisor

    BTW. arc_cot(x) does equal arc_tan(1/x), so perhaps that is what you were thinking?
     
  6. Jul 20, 2012 #5
    Nope I did it wrong...

    I went from 1 + tan2A = tan2A

    instead of going from 1 + tan2A = sec2A

    Which messed up my entire question.
     
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