Integral with a root in the denominator

In summary, the conversation discusses the process of solving an integral involving a variable in the denominator under a square root. The suggested substitution of z=s*tan(theta) is used, but there is confusion about the notation and connection to the final answer. After clarifying the notation and using the identity 1+tan^2(theta)=sec^2(theta), the integral is simplified and solved successfully. Another suggestion of z=s*sinh(theta) is also mentioned.
  • #1
Don'tKnowMuch
21
0

Homework Statement



I have been hung up on this integral: (μ /4∏ε) ∫ dz/(√s^2 + z^2)

Homework Equations





The Attempt at a Solution



i have tried a couple of different u-substitutions, and none are getting me anywhere. I do not that partial fractions, or by parts would help either. I know what the integral equals (integral table), but i should like to know how to calculate it.
 
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  • #2
the whole denominator is under the square root.
 
  • #3
Did you try the substitution,

[tex]z=s\cdot tan\theta[/tex]

The integral will be reduced to the integral of a single trigonometric ratio...
 
  • #4
I used the substitution that you suggested to get...

(μ/4∏ε)(1/s) ∫ dz/[√1+√tan^2(θ)]

I know the answer i should get is...

(μ/4∏ε) Ln[ z+√s^2+√z^2] (evaluated at the bounds...i think i can do that part)

I do not see the connection between your suggestion and the expression above (i.e. how does one get a Ln[stuff] term from trig).
 
  • #5
Keep going. Finish the substitution and simplify.
 
  • #6
Don'tKnowMuch said:
I used the substitution that you suggested to get...

(μ/4∏ε)(1/s) ∫ dz/[√1+√tan^2(θ)]
...

I do not see the connection between your suggestion and the expression above (i.e. how does one get a Ln[stuff] term from trig).
If [itex]z=s\,\tan(\theta)\,,[/itex] then what is [itex]dz\ ?[/itex]

The denominator should be [itex]\sqrt{1+\tan^2(\theta)}\,,[/itex] which is not the same as [itex]\sqrt{1}+\sqrt{\tan^2(\theta)}\,.[/itex]
 
  • #7
First off, thanks for the attention. I truly appreciate it! Sammy, yes you're right about the notation, I'm with you on that. dz should be s*(sec^2(theta))
 
  • #8
Don'tKnowMuch said:
First off, thanks for the attention. I truly appreciate it! Sammy, yes you're right about the notation, I'm with you on that. dz should be s*(sec^2(theta))
Then use the identity, [itex]1+\tan^2(\theta)=\sec^2(\theta)[/itex] & simplify.
 
  • #9
I"ve got it! Sheesh, it's like i removed splinter. Thank you so much. I love physics forums.
 
  • #10
Just another suggestion for the substitution: [tex]z=s.\sinh \theta[/tex]
 

Related to Integral with a root in the denominator

1. What is an "integral with a root in the denominator"?

An integral with a root in the denominator is a type of integration problem where the integrand (the expression inside the integral sign) contains a square root in the denominator. These types of integrals can be more challenging to solve compared to other types of integrals.

2. How do I solve an integral with a root in the denominator?

There are several methods for solving integrals with roots in the denominator, such as substitution, integration by parts, or using trigonometric identities. The most effective method will depend on the specific integral and its complexity.

3. Why are integrals with roots in the denominator important?

Integrals with roots in the denominator are important because they frequently arise in physics, engineering, and other fields of science. They can be used to solve problems related to velocity, acceleration, and other physical quantities.

4. Are there any special techniques for solving integrals with roots in the denominator?

Yes, there are some special techniques that can be used for solving integrals with roots in the denominator. For example, the substitution method is often used to simplify the integrand and make it easier to integrate.

5. Can integrals with roots in the denominator have multiple solutions?

Yes, integrals with roots in the denominator can have multiple solutions. This is because there may be more than one way to simplify the integrand and solve the integral. It is important to check for multiple solutions and choose the most appropriate one for the given problem.

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