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Integrating sqrt(x^2+1)/x^2 using trig

  • Thread starter dtl42
  • Start date
116
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1. Homework Statement

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

2. Homework Equations

3. The Attempt at a Solution
I tried a Trig Substitution with x=tan(u) and ended up with [tex]\int (csc(u))^{2} * sec(u) du[/tex]

From here I am kind of stuck. I tried a few different integration by parts methods, but they got very messy. I also couldn't find any sort of table for this.
 

Answers and Replies

tiny-tim
Science Advisor
Homework Helper
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I tried a Trig Substitution with x=tan(u) and ended up with [tex]\int (csc(u))^{2} * sec(u) du[/tex]
Hi dtl42! :smile:

Yes, you're almost there …

Put cosec^2 = 1 + cot^2, and you have:
[tex]\int \left(sec(u)\,+\,cot(u)csc(u)\right) du\,.[/tex] :smile:

(though personally, I'd have used x = sinhv, giving ∫coth^2(v)dv)
 
116
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Thanks very much, I can't believe I didn't see that. Its those variations of the Pythag. Identity that get me.
 

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