Approximating an E&M Integral with Calculus

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SUMMARY

The forum discussion focuses on approximating an electromagnetic (E&M) integral using calculus, specifically evaluating the expression B_0(∫_{-H_{max}}^{H_{max}}{tanh((H+H_c)/H_0)dH} - ∫_{-H_{max}}^{H_{max}}{tanh((H-H_c)/H_0)dH}). Participants confirm that H_c and H_0 are constants and suggest using the integral of tanh, which is ln(cosh), to simplify the problem. The discussion emphasizes the importance of recognizing that the second integral is the additive inverse of the first, allowing for simplification and approximation based on the condition H_{max} >> H_c, H_0.

PREREQUISITES
  • Understanding of calculus, specifically integral calculus.
  • Familiarity with hyperbolic functions, particularly tanh.
  • Knowledge of the properties of logarithmic functions, especially ln(cosh).
  • Concept of limits and approximations in mathematical analysis.
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  • Study the properties and applications of hyperbolic functions in calculus.
  • Learn techniques for simplifying integrals involving hyperbolic functions.
  • Explore the concept of asymptotic analysis in mathematical approximations.
  • Review the derivation and applications of the integral of tanh in physics problems.
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Students and professionals in physics and engineering, particularly those dealing with electromagnetic theory and integral calculus, will benefit from this discussion.

Matterwave
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Homework Statement


This is technically an E&M question, but I've reduced it to a calculus problem. Basically I have to evaluate:

[tex]B_0(\int_{-H_{max}}^{H_{max}}{tanh(\frac{H+H_c}{H_0})dH - \int_{-H_{max}}^{H_{max}}{tanh(\frac{H-H_c}{H_0})dH)[/tex]

Where [tex]H_{max}>>H_C, H_0[/tex].

Homework Equations


The Attempt at a Solution



I'm looking at this and I have no idea how to go about approximating this integral...I suppose I could just brute force the integrals and keep all the H_max and stuff, and then later see if i can approximate something...but the expressions are really quite long and I'd like to avoid that if I can. Is there a way?
 
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Hi Matterwave! :smile:

Are Hc and H0 constants?

If so, that's just ∫tanh(Ax + b) dx …

and ∫tanh is ln(cosh) :wink:
 
You can eliminate the second integral (it's just the additive inverse of the first; prove it). Per tiny-tim's hint, you can compute the integral. Simplify and finally use the fact that Hmax>>Hc , H0 to arrive at an approximate value.
 

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