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

In summary, the conversation discussed the integration of \int\frac{\sqrt{x^{2}+1}}{x^{2}} dx using Trig Substitution, which resulted in \int (csc(u))^{2} * sec(u) du. It was suggested to use the Pythagorean Identity to simplify the integral.
  • #1
dtl42
119
0

Homework Statement



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

Homework Equations



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.
 
Physics news on Phys.org
  • #2
dtl42 said:
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)
 
  • #3
Thanks very much, I can't believe I didn't see that. Its those variations of the Pythag. Identity that get me.
 

1. What is the formula for integrating sqrt(x^2+1)/x^2 using trig?

The formula for integrating sqrt(x^2+1)/x^2 using trig is: ∫(sqrt(x^2+1)/x^2)dx = ln|x+sqrt(x^2+1)|+C.

2. Why is trigonometry used to integrate sqrt(x^2+1)/x^2?

Trigonometry is used because it provides a way to simplify the expression sqrt(x^2+1)/x^2 into a more manageable form. By using trigonometric identities, we can rewrite the expression as a combination of trigonometric functions, which can then be integrated using standard techniques.

3. What is the domain of the integrand sqrt(x^2+1)/x^2?

The domain of sqrt(x^2+1)/x^2 is all real numbers except for x=0, as dividing by 0 is undefined. This means that the integral can be evaluated for any value of x except 0.

4. Can the integral of sqrt(x^2+1)/x^2 be evaluated using substitution?

Yes, the integral can be evaluated using substitution. By substituting u = x+sqrt(x^2+1), we can rewrite the integrand as 1/u and use the rule for integrating 1/u to find the solution.

5. Is there a geometric interpretation of the integral of sqrt(x^2+1)/x^2?

Yes, there is a geometric interpretation of the integral. The integral represents the area under the curve of the function sqrt(x^2+1)/x^2 from x=0 to x=∞. This can be visualized as the area of an infinite triangle with base x and height sqrt(x^2+1), which is equal to ln|x+sqrt(x^2+1)|+C.

Similar threads

  • Calculus and Beyond Homework Help
Replies
22
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
343
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
  • Calculus and Beyond Homework Help
Replies
8
Views
762
  • Calculus and Beyond Homework Help
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
9
Views
723
  • Calculus and Beyond Homework Help
Replies
12
Views
1K
  • Calculus and Beyond Homework Help
Replies
2
Views
870
  • Calculus and Beyond Homework Help
Replies
27
Views
3K
  • Calculus and Beyond Homework Help
Replies
15
Views
784
Back
Top