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Are these two integral formulas the same?

  1. Sep 26, 2007 #1
    In my book, we were give:

    int of tanx dx = - ln|cos x| + c

    and later I cam across:

    int of tanx dx = ln |sec x| + c

    --should I use these interchangeably or what?
  2. jcsd
  3. Sep 26, 2007 #2

    D H

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    What is the relation between [itex]\cos x[/itex] and [itex]\sec x[/itex]?
  4. Sep 26, 2007 #3
    [tex]ln\left(\frac{1}{x}\right) = -ln x \quad \textrm{and} \quad \sec x = \frac{1}{\cos x}[/tex]

    So yes, you can use them interchangeably.
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