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Simple question of calculus

  1. Aug 24, 2013 #1
    1. The problem statement, all variables and given/known data

    differentiate with respect to x

    2. Relevant equations


    3. The attempt at a solution

    i have simplified it by substituting cos2x as 1-2sin2x and 2cos2x-1

    I have got the answer as sec2x but my textbook says the ans is [itex]\frac{tanx}{|tanx|}[/itex]sec2x

    plz help
  2. jcsd
  3. Aug 24, 2013 #2


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    Homework Helper

    Your answer is correct. I don't see the need for your book to specify tanx/tanx in it.
  4. Aug 24, 2013 #3
    it is tanx/|tanx|
    the denominator is mod of tanx
  5. Aug 24, 2013 #4


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    Homework Helper

    Yes well the main point was that for x>0, |tanx| = tanx so it would cancel out to give you sec2x.

    The only reason I can think of to specify something like that is if you accounted for taking the square root of the radical.

    Meaning that your expression would simplify to √(tan2x) = ± tanx

    and d/dx(± tanx) = ± sec2x
  6. Aug 24, 2013 #5
    thanks got it
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