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Re: variables versus functions

  • To: mathgroup at
  • Subject: [mg28808] Re: variables versus functions
  • From: "Orestis Vantzos" <atelesforos at>
  • Date: Mon, 14 May 2001 01:33:00 -0400 (EDT)
  • Organization: National Technical University of Athens, Greece
  • References: <9dld6m$>
  • Sender: owner-wri-mathgroup at

Well A=Cos[x] will always be the Cosinus of x, whereas A[x_]:=Cos[x]  is the
abstract concept of Cosinus, so that A[t]=Cos[t],A[2]=Cos[2] etc.
FindRoot[A==B,...] would simply not work since A[x_]:=Cos[x] does not mess
around with the symbol A itself (A will still evaluate to A, not Cos[...]).
FindRoot[A[x]==B[x],{x,pi/2}] would work like a charm though...and so would
FindRoot[A[t]==B[t],{t,pi/2}] which takes us back to your first question.

PS. You can think of A=Cos[x] as an EXPRESSION (something that simply is),
whereas A[x_]:=Cos[x] defines a FUNCTION (something that does something).

"Julian Sweet" <jsweet at> wrote in message
news:9dld6m$o9g at
> How is it different to define a variable such as A=Cos[x]
> versus a function  A[x_]:=Cos[x] ?
> Furthermore, what If I define two functions  A[x_]:=Cos[x] and
> B[x_]=ArcTan[x]?  How would FindRoot[A==B,{x,pi/2}]  treat this
> differently than if I just used variable definitions for A & B?
> e-mail response appreciated: jsweet at

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