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Re: large integration result for simple problem: 1/x,, also BesselJ

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  • Subject: [mg122844] Re: large integration result for simple problem: 1/x,, also BesselJ
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Sat, 12 Nov 2011 07:34:02 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Integrate[BesselJ[n, b*x], {x, 0, Infinity}, Assumptions -> Re[n] > -1]
Simplify@PowerExpand@%

b^(-2 + n) (b^2)^(1/2 - n/2)

1/b

Bobby

On Fri, 11 Nov 2011 03:55:15 -0600, Richard Fateman  
<fateman at cs.berkeley.edu> wrote:

> (at least in Mathematica 7.0)
>
> try
>
> Integrate[1/x,{x,a,b}]
>
> Also
>
> Integrate[BesselJ[n, b*x], {x, 0, Infinity},   Assumptions -> Re[n] > -1  
> ]
>
> which returns an expression including this ....
>
> b^(-2 + n) (b^2)^(1/2 - n/2)
>
> which should be possible to simplify.  For example, for b>0, the
> expression is 1/b.
>
> maybe  1/b * If[b>0, 1 ,  -(-1)^n]  or so.
>
> I've been playing with integration of expressions involving Bessel
> functions.  Mathematica is sometimes surprising, on both sides of the
> ledger -- (Yes we Can and No we Can't).
>
>
> RJF
>
>


-- 
DrMajorBob at yahoo.com



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