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Re: integration

  • To: mathgroup at smc.vnet.net
  • Subject: [mg95972] Re: [mg95952] integration
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Sat, 31 Jan 2009 01:13:32 -0500 (EST)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200901301047.FAA06620@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

Both answers -- yours and the Wolfram Mathematica Online Integrator's -- 
are correct.  If you take the derivative of both, you'll see they are 
the same at least when b > 0, and at least for some domain of values of x.

t.p.nixon at open.ac.uk wrote:
> Hi, I don't use mathematica but the other day I wanted to solve an
> integral and I'm out of practice so I went on-line to a mathematica
> based integrator.
> 
> http://integrals.wolfram.com/index.jsp
> 
> I typed in 1/sqrt(x^2-b^2) this should have an integral of cosh^-1(x/
> b).  Ok, so it didn't recognize cosh but its answer was (I think)
> wrong.  it comes back with ln(x+sqrt(x^2-b^2)) it seems to have
> overlooked a quotient of b in the log.
> 
> Is this a general problem with mathematica or just the on-line version
> or is it me?
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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