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MathGroup Archive 2006

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Re: simplify a trig expression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg65483] Re: simplify a trig expression
  • From: "David W. Cantrell" <DWCantrell at sigmaxi.org>
  • Date: Wed, 5 Apr 2006 06:55:22 -0400 (EDT)
  • References: <200603311109.GAA15029@smc.vnet.net> <200604011038.FAA07301@smc.vnet.net> <200604020900.FAA01612@smc.vnet.net> <11D40ADD-9EC9-4DCE-B685-1CA00605B9B2@mimuw.edu.pl> <e0r0c9$mt$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Murray Eisenberg <murray at math.umass.edu> wrote:
> Actually, what I was trying to do is this:  To obtain in Mathematica,
> the answers to a ten-question integration exam that would be of the form
> students would obtain with standard paper-and-pencil techniques.  And
> the purpose of that was to to provide to the graders, whom I supervise,
> answers that are unquestionably correct -- and, again, in that form.

But surely this endeavor is doomed to failure. Consider the simple example,
which happens to be closely related to your earlier ones:

Integrate[1/x, x]

Mathematica will give just Log[x], which is perfectly correct. But I
presume that you want your students to give Log[Abs[x]] plus an arbitrary
constant of integration. How might one get Mathematica to give Log[Abs[x]]?
I certainly don't know how.

It seems to me that you should give your graders _one form_ of correct
answer for each problem and that you must then depend on their mathematical
intelligence to recognize alternative correct forms. If you can't depend on
that, are they really qualified to be graders?

Regards,
David Cantrell


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