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MathGroup Archive 2005

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Re: Simplify[expr] bug?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53408] Re: [mg53398] Simplify[expr] bug?
  • From: Ken Tozier <kentozier at comcast.net>
  • Date: Mon, 10 Jan 2005 01:42:02 -0500 (EST)
  • References: <200501100404.XAA14039@smc.vnet.net> <41E21453.1080603@math.umass.edu>
  • Sender: owner-wri-mathgroup at wolfram.com

On Jan 10, 2005, at 12:36 AM, Murray Eisenberg wrote:

> 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.

Duly chastised : )

I come from a C background so the "(" and ")" looked like a perfectly 
reasonable way to call a function. It's just one of those blind spot 
things.

Thanks for the info.

Ken

>
>
> 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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