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MathGroup Archive 2005

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Re: Simplify[expr] bug?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53407] Re: [mg53398] Simplify[expr] bug?
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Mon, 10 Jan 2005 01:42:00 -0500 (EST)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200501100404.XAA14039@smc.vnet.net>
  • Reply-to: murray at math.umass.edu
  • Sender: owner-wri-mathgroup at wolfram.com

NO, it's not a bug!

Before attempting such things, it behooves you to read a couple of pages 
of the documentation that accompanies Mathematica.  Just about ANY 
source of such documentation would explain that (in the default input 
mode for Mathematica expressions), you surround arguments of functions 
in [square brackets], whereas (parentheses) are used solely as punctuation.

What you entered means:  Sin * a - Sin * b.  so Mathematica correctly 
simplfied that by factoring out the expression Sin.

What presumably you want to enter is:

   Simplify[Sin[a] - Sin[b]]

But since Mathematica knows nothing about a or b, it will return
  Sin[a] - Sin[b] as result.

The same problem is the case with your second alleged bug.

Plesae try not to suggest attributing the term "bug" to Mathematica 
behavior you do not yet understand!

Best wishes for getting started productively with Mathematica.


Ken Tozier wrote:
> I'm a complete newbie to Mathematica and not a math whiz, but the 
> results I got from the following two equations seems like bugs to me.
> 
> Test 1:
> Running: Simplify[Sin(a) - Sin(b)]
> Yeilds: (a - b)Sin
> 
> Looks like it's treating the function "Sin" like a coefficient
> 
> Test 2:
> Running: Simplify[d/s + Cos(2*¹*v/s) - Cos(2*¹*(v - 1)/s)]
> Yeilds: (d + 2 Cos ¹) / s
> 
> Mathematica completely factors out the variable "v" which is critical 
> to the correct solution.
> 
> Are these bugs or am I making an inadvertent syntax error.
> 
> Thanks,
> 
> Ken Tozier
> 
> 

-- 
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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