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Homework Help: Finding an integral

  1. Apr 5, 2008 #1
    1. The problem statement, all variables and given/known data

    I would just like some help on how to find the integral of:
    sin(x) / cos(x)^2



    2. Relevant equations

    integration by parts?
    uv-integral of v(du)


    3. The attempt at a solution
    I tried using integration of parts with u = cos(x)^2 and dv = sin(x) but I just got myself in a bigger mess.

    I noticed that sin(x) / cos(x)^2 was equal to tan(x)sec(x). Not sure if that helps though...

    Help please?!
     
  2. jcsd
  3. Apr 5, 2008 #2
    I'd go for a substitution.
     
  4. Apr 5, 2008 #3
    Try the substitution cos(x)^2.
     
  5. Apr 5, 2008 #4
    what's integral of [(-2*u)/(1-u^2)]/-2

    or

    try to see 1/x connection
     
    Last edited: Apr 5, 2008
  6. Apr 5, 2008 #5

    rock.freak667

    User Avatar
    Homework Helper

    [tex]\int \frac{sinx}{cos^2x} dx[/tex]

    [tex]\equiv \int \frac{sinx}{cosx} \times \frac{1}{cosx}dx[/tex]

    What is another way to write [itex]\frac{sinx}{cosx}[/itex]?
    and similarly [itex]\frac{1}{cosx}[/itex]?


    Should be pretty standard after you see it.
     
  7. Apr 6, 2008 #6
    Got it. Thank you everyone.
     
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