MathGroup Archive 1997

[Date Index] [Thread Index] [Author Index]

Search the Archive

RE: Integration bugs in Mathematica 3.0

  • To: mathgroup at smc.vnet.net
  • Subject: [mg9341] RE: [mg9213] Integration bugs in Mathematica 3.0
  • From: "Richard W. Finley, M. D." <trfin at umsmed.edu>
  • Date: Sat, 1 Nov 1997 03:33:27 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Carlos
I use Mathematica 3.01 under Win95.  Performing the definite integral
you give as fu, Mathematica gives  the answer (after simplifying):  BQ
=  Sqrt[2](2 + Cos[phiQ]) EllipticK[-2 - 2/(1+Cos[phiQ])]Sqrt[3 +
Sec[phiQ/2]^2]/(5+3 Cos[phiQ])

And BQ/.phiQ->0  gives 3 EllipticK[-3] = 3.23477  which I believe is the
correct answer....??

I don't see the problem.  Are you using version 3.00  ?  Perhaps this is
something that was fixed in the update?

RF

-----Original Message-----
From:	Carlos A. Felippa [SMTP:carlos at mars.Colorado.EDU] To:
mathgroup at smc.vnet.net
Sent:	Friday, October 24, 1997 12:00 AM To:	mathgroup at smc.vnet.net
Subject:	[mg9213] Integration bugs in Mathematica 3.0

In a recent FEM project assigned as HW, about one third of the Integrate
results (216 out of roughly 600)  were wrong.   Extracted sample:

fu=(2+Cos[phiQ])/Sqrt[6-2*Cos[phiQ]*(-2+Cos[theta])-4*Cos[theta]];
BQ=Integrate[fu,{theta,0,Pi}]; 
Print["BQ=",BQ//InputForm];
fu=fu/.{phiQ->0};
BQ=Integrate[fu,{theta,0,Pi}]; 
Print["BQ=",BQ//InputForm];

Results:

BQ=0   (* wrong *)
BQ=3*EllipticK[-3]  (* demonstrates bug *)

The students were not amused.  2.2 does it right, but most of them did
not have access to it on campus machines.

Further, Integrate takes 2-5 times longer than in 2.2.



  • Prev by Date: logarithmic graphics
  • Next by Date: Possibly Silly Question on Manipulating Statistical Distributions
  • Previous by thread: Re: logarithmic graphics
  • Next by thread: Possibly Silly Question on Manipulating Statistical Distributions