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MathGroup Archive 2000

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Re: Simple equation checking..

  • To: mathgroup at
  • Subject: [mg25654] Re: Simple equation checking..
  • From: Yossi Lonke <jrl16 at>
  • Date: Wed, 18 Oct 2000 02:52:26 -0400 (EDT)
  • Organization: Dept. Mathematics, CWRU
  • References: <8seb1e$>
  • Sender: owner-wri-mathgroup at


The derivative you calculated by hand is not correct, so not only
don't the results look the same, they are in fact not the same.
In general, a robust way is to use Simplify[a-b] where a is your expression
and b is Mathematica's expression. In most cases (algebraic functions for
the simplification would yield zero when the two expressions are the same.

Yossi Lonke

Ian Fan wrote:

> Hi again, thanks for all the help with my last question but now I am stuck
> with another problem if anyone would be so kind enough to help.
> I am looking for a way to check equations, for example, the derivative of
> ((x^3 - 4x + 3)/x^(4/3) is (5x^(10/3) - 8x^(7/3) - 12x^(1/3))/(3x^(8/3))
> when calculated via hand but is (3x^2 - 4)/x^(4/3) - 4(x^3 - 4x +
> 3)/(3x^(7/3)) when put through mathematica. What I would like to do is if
> there is any way to equate the two and see if the statement is true because
> obviously it can look like two completely different answers (to a student)
> when they are in fact the same.
> Another example would be, is there any way to check if E^(:ii:Pi) = -1 was
> true (at least according to the Euler-Moivre equation), using Mathematica?
> I tried using the "Check" command but I don't know what two arguments there
> are (I tried putting in lhs,rhs but I just got the former as an output).
> Thanks in advance,
> Ian Fan

Dr. Yossi Lonke
Mathematics Department
Case Western Reserve University
10900 Euclid Avenue
Cleveland, Ohio 44106
216 368-5423

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