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Thread Subject:
solutions parametrised by symbols in solve at 180

Subject: solutions parametrised by symbols in solve at 180

From: asher

Date: 19 Sep, 2013 12:45:09

Message: 1 of 4

Hi,
Please do you know how to handle the warning "The solutions are parametrized by the symbols" "In solve at 180"? I want to obtain a numeric solution for N in the following problem:

% These are known scalars stored in the workspace
[e1, c1, eta, c2]'
ans =
    2.3122
    0.0076
    0.5000
    0.0543

% Try to solve for N
syms N
solve((N^e1)+c1*(N^(eta+1))-c2,N)

Warning: The solutions are parametrized by the symbols:
z2 = RootOf(z^911 + (136753569599747*z^591)/18014398509481984 -
7819197184492677/144115188075855872, z)
> In solve at 180
 
ans =
z2^394

From elsewhere I know that N should be something like 0.2894, I just don't know how to obtain it. I have Matlab R2012b (and symbolic math toolbox 5.9). Please is there a way out? Thank you for helping!

Subject: solutions parametrised by symbols in solve at 180

From: Ralf Hillebrand

Date: 19 Sep, 2013 13:53:06

Message: 2 of 4

Tell MATLAB, that you are not interested in complex solutions by
restricting N to be real:

 >> e1 = 2.3122;
 >> c1 = 0.0076;
 >> eta = 0.5000;
 >> c2 = 0.0543;
 >> syms N real;
 >> solve((N^e1)+c1*(N^(eta+1))-c2,N)

ans =

0.2810968999997302684663091406561


On 09/19/13 14:45, asher wrote:
> Hi,
> Please do you know how to handle the warning "The solutions are
> parametrized by the symbols" "In solve at 180"? I want to obtain a
> numeric solution for N in the following problem:
>
> % These are known scalars stored in the workspace
> [e1, c1, eta, c2]'
> ans =
> 2.3122
> 0.0076
> 0.5000
> 0.0543
>
> % Try to solve for N
> syms N
> solve((N^e1)+c1*(N^(eta+1))-c2,N)
>
> Warning: The solutions are parametrized by the symbols:
> z2 = RootOf(z^911 + (136753569599747*z^591)/18014398509481984 -
> 7819197184492677/144115188075855872, z)
>> In solve at 180
>
> ans = z2^394
>
> From elsewhere I know that N should be something like 0.2894, I just
> don't know how to obtain it. I have Matlab R2012b (and symbolic math
> toolbox 5.9). Please is there a way out? Thank you for helping!

Subject: solutions parametrised by symbols in solve at 180

From: asher

Date: 19 Sep, 2013 15:59:07

Message: 3 of 4

> Tell MATLAB, that you are not interested in complex solutions by
> restricting N to be real:
>
> >> e1 = 2.3122;
> >> c1 = 0.0076;
> >> eta = 0.5000;
> >> c2 = 0.0543;
> >> syms N real;
> >> solve((N^e1)+c1*(N^(eta+1))-c2,N)
>
> ans =
>
> 0.2810968999997302684663091406561

Hello, thank you so much for answering! Though, I have a problem: when I do like you, I still get the same type of warning, though this time the expression is at least much shorter. Still, I don't arrive at any numeric value. Any further hints? Much appreciated. Thank you.

Subject: solutions parametrised by symbols in solve at 180

From: Nasser M. Abbasi

Date: 19 Sep, 2013 18:05:46

Message: 4 of 4

On 9/19/2013 10:59 AM, asher wrote:
>> Tell MATLAB, that you are not interested in complex solutions by
>> restricting N to be real:
>>
>> >> e1 = 2.3122;
>> >> c1 = 0.0076;
>> >> eta = 0.5000;
>> >> c2 = 0.0543;
>> >> syms N real;
>> >> solve((N^e1)+c1*(N^(eta+1))-c2,N)
>>
>> ans =
>>
>> 0.2810968999997302684663091406561
>

  
> Hello, thank you so much for answering! Though, I have a problem:
>when I do like you, I still get the same type of warning, though this
>time the expression is at least much shorter. Still, I don't arrive at any
>numeric value. Any further hints? Much appreciated. Thank you.
>

This does not happen in 2013a. So, you can upgrade. It seems like something
that was fixed.

--Nasser

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