How Do You Integrate a Product of Bessel Functions with Polynomial Denominators?

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SUMMARY

The discussion centers on finding the antiderivative of the function \( f(x) = \frac{J_{0}(ax)J_{1}(bx)}{x+x^{4}} \), where \( J_{0} \) and \( J_{1} \) are Bessel functions of the first kind and \( a \) and \( b \) are constants. A user seeks to derive a formula for pavement deflections from traffic loads, expressed as \( d(x) = \int_0^\infty \frac{J_{0}(atx)J_{1}(bt)}{t+t^{4}} \, dt \), and aims to compute the second derivative \( \frac{d^2d(x)}{dx^2} \). The solution involves differentiating the first Bessel function with respect to \( x \) rather than attempting to find the antiderivative first.

PREREQUISITES
  • Understanding of Bessel functions, specifically \( J_{0} \) and \( J_{1} \).
  • Knowledge of integral calculus, particularly techniques for evaluating improper integrals.
  • Familiarity with differentiation under the integral sign.
  • Basic understanding of pavement engineering concepts related to traffic loads.
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  • Research the properties and applications of Bessel functions in engineering contexts.
  • Study techniques for differentiation under the integral sign in calculus.
  • Learn about the implications of pavement deflections and their calculations in civil engineering.
  • Explore numerical methods for evaluating integrals involving special functions like Bessel functions.
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Mathematicians, civil engineers, and researchers involved in applied mathematics, particularly those working with Bessel functions and their applications in engineering problems related to pavement analysis.

oh20elyf
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I am struggling to find the antiderivative of the following function:f(x)=\frac{J_{0}(ax)J_{1}(bx) }{x+x^{4} } <br /> \\<br /> J_{0},{~}J_{1} : Bessel{~}function{~}of{~}the{~}first{~}kind\\<br /> a, b: constants<br /> \\<br /> F(x)=\int_{}^{} \! f(x) \, dx =?Who can help?
 
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oh20elyf said:
I am struggling to find the antiderivative of the following function:f(x)=\frac{J_{0}(ax)J_{1}(bx) }{x+x^{4} } <br /> \\<br /> J_{0},{~}J_{1} : Bessel{~}function{~}of{~}the{~}first{~}kind\\<br /> a, b: constants<br /> \\<br /> F(x)=\int_{}^{} \! f(x) \, dx =?Who can help?

What is the context of the question? Should the answer be in terms of the Bessel function?
 
ZaidAlyafey said:
What is the context of the question? Should the answer be in terms of the Bessel function?

Ok so the root of my problem is that i have a formula to calculate pavement deflections from traffic loads, which is the following:

d(x)=\int_0^\infty \! \frac{J_{0}(atx)J_{1}(bt)}{t+t^{4} } \, d t

a,b: constants
x: distance from load centre

Now i want to find a formula to calculate the acceleration. I have to find the second derivative of the above formula with respect of 'x'.

To do so i thought i had to get rid of the integral at first, by finding the antiderivative with respect of 't' of the equation first to be able to differentiate with respect of 'x' twice. Is there a better way to find:

\frac{d^2d(x)}{dx^2}=?
 
Last edited:
Well, the only place the $x$ shows up is in the first Bessel function inside the integral. It's not even present in the limits of the integral. So, just differentiate that first Bessel function twice with respect to $x$, and you're done.
 

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