How to deal with this integral
- To: mathgroup at smc.vnet.net
- Subject: [mg97783] How to deal with this integral
- From: paperkite rainyday <paperkite at gmail.com>
- Date: Sat, 21 Mar 2009 05:19:41 -0500 (EST)
hi everybody,
I want to deal with this integral with Mathematica:
Integrate[a*b*Exp[-(a+b)]*DiracDelta[1/(4*a)+1/(4*b)+c-t],{a,0,Infinity},{b,0,Infinity},{c,0,Infinity},Assumptions->t>0],
Mathematica 6.0 gives 0. But it is wrong, the correct result is
(1/2)*x^2*Exp[-x]*((1+x)*BesselK[0,x]+(2+x+2/x)*BesselK[1,x]),
where x=1/(2*t).
What's wrong?
Thanks,
paperkite