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## Using fsolve to solve example problem from documentation gives very diff

 From: Steven Davis Subject: Using fsolve to solve example problem from documentation gives very different result Date: Wed, 14 Oct 2015 11:40:46 -0500

Hi,

I was trying to use fsolve to solve a system of equations, and couldn't get it to work.  So I decided to try entering the example from the Octave documentation, Chapter 20 page 505. I figured once I got that to run I could work my way through to figure out what I was doing wrong.  But I couldn't get fsolve to give the same result the documentation example said I should get!

I entered into the editor and saved as f.m the following:

function y=f(x)
y=zeros(2,1);
y(1)=-2*x(1)^2+3*x(1)*x(2)+4*sin(x(2))-6;
y(2)=3*x(1)^2-2*x(1)*x(2)^2+3*cos(x(1))+4;
endfunction

I then entered into the command window:

[x,fval,info]=fsolve(@f,[1;2])

According to the documentation I should get:

x =
0.57983
2.54621
fval =
-5.7184e-10
5.5460e-10
info = 1

[x,fval,info]=fsolve(@f,[1;2])
y =

0
0

y =

0
0

y =

0
0

y =

0
0

y =

0
0

warning: matrix singular to machine precision
warning: called from
fsolve>__dogleg__ at line 587 column 5
fsolve at line 303 column 11
y =

0
0

x =

1
2

fval =

0
0

info = -3
>> f
y =

0
0

ans =

0
0

I don't know where to start resolving this, I could use some help.