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Re: Dumb question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg27788] Re: [mg27772] Dumb question
  • From: Tomas Garza <tgarza01 at prodigy.net.mx>
  • Date: Sat, 17 Mar 2001 05:41:12 -0500 (EST)
  • References: <200103140907.EAA00012@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

I'm afraid there is no such discontinuity at x = a. To see this, take

In[1]:=
p = (Sin[a - x]*t/(a - x))^2;

(there is a convention in Mathematica that all user-defined symbols or
functions should start with a lower-case letter, so as not to clash with
built-in functions, which always begin with upper-case; also, the use of
square brackets [] is restricted to functions and commands). Then you have

In[2]:=
Limit[p, x -> a, Direction -> 1]
Out[2]=
t^2

In[3]:=
Limit[p, x -> a, Direction -> -1]
Out[3]=
t^2

(check The Book or the on-line help browser to know more about the option
Direction in Limit) and so, by definition the function p is continuous at x
= a, for any choice of t. Then there should be no problem to obtain its
graph, for any particular values of t and a. E.g.,

In[4]:=
Plot[p /. {t -> 1, a -> Pi/2}, {x, 0, Pi}];

where the rules "->", together with "ReplaceAll" (abbreviated as "/.") are a
way of substituting particular values in the function p.

Tomas Garza
Mexico City


----- Original Message -----
From: "Gustavo Seabra" <gseabra at swbell.net>
To: mathgroup at smc.vnet.net
Subject: [mg27788] [mg27772] Dumb question


> Hello. I know this may be a dumb question, and I apologize for doing that.
> But I am new to Mathematica, and I'm having a little trouble with this. I
> want to plot the equation:
>
> P=[sin(a-x)*t/(a-x)]^2
>
> with fixed t (say, 1) and fixed a (say, Pi/2), with x varying from 0 to
Pi.
> I know there is a discontinuity at x=a. Is there a way to plot this? I
mean,
> P(x) versus x?
>
> Thanks,
> --
> -----------------------------------------------------------------
> Gustavo Seabra - Graduate Student
> Chemistry Department
> Kansas State University
> -----------------------------------------------------------------
>
>



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