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Help with basic integral

  1. Jan 14, 2012 #1
  2. jcsd
  3. Jan 14, 2012 #2

    Curious3141

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    Homework Helper

    What have you tried?

    You have to show work before any help is given. From the FAQ:

     
  4. Jan 14, 2012 #3
    hey curious,
    can how show my effort to solve this exercise?

    i am not know to solve this integral, because i ask help please.
     
  5. Jan 14, 2012 #4

    Mentallic

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    You can show what you've tried by typing it out step by step, for example:

    x2-2=0
    x2=2
    x= +/- sqrt(2)

    or better yet, use Latex!

    [tex]x^2-2=0[/tex]
    [tex]x^2=2[/tex]
    [tex]x=\pm\sqrt{2}[/tex]

    These can be written as follows (taking out the spaces in the tex tags)

    [ tex]x^2-2=0[ /tex]
    [ tex]x^2=2[ /tex]
    [ tex]x=\pm\sqrt{2}[ /tex]

    For integrals, use

    [tex]\int{\frac{x}{x^2+1}}[/tex]

    [ tex]\int{\frac{x}{x^2+1}}[ /tex]

    If you ever see latex being used and want to know how to type it yourself, you can quote that message and in the quote it will show you the text required.

    For the first two, think about using this technique:

    [tex]\frac{a}{a+b}=\frac{a+b-b}{a+b}=1-\frac{b}{a+b}[/tex]
     
  6. Jan 14, 2012 #5

    Curious3141

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    That was the *exact* hint I was thinking about providing before I decided to wait for TS' reply first and went offline. *Exact*, word for word, same symbols and everything. You ARE a mindreader, Mentalist, oops, Mentallic. :rofl:

    Stud: This is a very good hint. For the first integral, you get an almost-immediate answer, without needing any substitution. The second integral, you can get an almost-immediate answer for it if you recognise a particular form (hint: derivative of [itex]\arctan{x}[/itex]). If not, you can try a [itex]x = \tan\theta[/itex] substitution on the second term after applying this trick.

    Mentallist, I or someone else can hint you along with the rest as well, but you HAVE to show some work here first. Deal? :smile:
     
    Last edited: Jan 14, 2012
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