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MathGroup Archive 2009

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Re: treatment on C[i]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg100314] Re: [mg100294] treatment on C[i]
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Mon, 1 Jun 2009 07:05:01 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

soln1 = y[x] /. DSolve[y''[x] == 4 y[x], y[x], x][[1]]

C[1]*E^(2*x) + C[2]/E^(2*x)

You can specify any parameter that you want

soln2 = y[x] /. 
  DSolve[y''[x] == 4 y[x], y[x], x, GeneratedParameters -> a][[1]]

a[1]*E^(2*x) + a[2]/E^(2*x)

Or you can use replacement

soln3 = soln1 /. C[n_] :> Symbol["a" <> ToString[n]]

a1*E^(2*x) + a2/E^(2*x)


Bob Hanlon

---- olfa <olfa.mraihi at yahoo.fr> wrote: 

=============
Hi mathematica community,
C[i] is the default form for the i th parameter or constant generated
by mathematica in representing the results of various symbolic
computations in such functions as DSolve, RSolve and Reduce.
My question is: is it possible to know in advance how many C[i]  will
be generated?
 If not how to represent the generic form of them: For example I have
an input with reduce and mathematica generates in the output C[1],C
[2],C[3] and C[4] so four C[i] in the solutions but before that when I
wrote the input I did not know that it will generate four C[i] and I
need to use something in the input that represent C[i] in general
without knowing how many of them will be generated? I have tried to
use the pattern object _  like that C[ _ ]  but it does not work.

Any suggestion?
Thank you very much.




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