What could be the reason for this fzero error and how to solve it ?

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VIGNESH BALAJI
VIGNESH BALAJI on 2 Feb 2024
Commented: VIGNESH BALAJI on 9 Feb 2024
This is the error message
This was the warning I got too along with the error message
This is the 5 lines of code to reproduce the error
dd = 0.1069;
vv = 0.7889;
L = 1;
fun = @(aa) ( (-(sqrt(L^2-(vv)^2)/2)) + (aa*sinh(((dd)/2)/aa)) ); xx0 = 0.15; %[10^-6, 10^6];
aa = abs(fzero(fun,xx0));
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Torsten
Torsten on 7 Feb 2024
If you look at the f(a) and f(b) values in your output, you can see that both are negative in all iterations. Thus fzero does not find a sign change and keeps on serching for suitable limits a and b for which f(a)*f(b) < 0 holds.
VIGNESH BALAJI
VIGNESH BALAJI on 9 Feb 2024
@Torsten thanks, I now understand the reason behidn fzero error. Both your answer and @Dyuman Joshi heped me to solve this problem. I am not sure how to accept both of your answers to close this thread.

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Answers (2)

Torsten
Torsten on 2 Feb 2024
Use "fsolve" instead of "fzero":
aa = fsolve(fun,xx0)
Matt J
Matt J on 2 Feb 2024
Edited: Matt J on 2 Feb 2024
Ran in:
You should plot the function to get a better idea where the solution is,
dd = 0.1069;
vv = 0.7889;
L = 1;
fun = @(aa) ( (-(sqrt(L^2-(vv)^2)/2)) + (aa*sinh(((dd)/2)/aa)) );
fplot(fun,[0.01,0.05])
Warning: Function behaves unexpectedly on array inputs. To improve performance, properly vectorize your function to return an output with the same size and shape as the input arguments.
fzero(fun,[0.01,0.05])
ans = 0.0142

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