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## Re: Problems with fzero

 From: Schloegl Alois Subject: Re: Problems with fzero Date: Thu, 31 Oct 2002 19:24:18 +0100 (MET) User-agent: IMP/PHP IMAP webmail program 2.2.8

```see

x=-10:.001:10;
y=x-1.09-2.7217*log(1+(x/2.7217));
plot(x,real(y'*[1,-i]))

Based on this graph, the solutions 3.2106 and -1.7701 are correct.
for all x<2.7217, y(x) is complex. It looks like FZERO (and FSOLVE) look only
for the real part of the function y(x). If y(x) has a non-zero imaginary part,
a warning (or error) message should appear.

Alois

> Hello all,
>     I have a BIG problem with fzero
>     I have a "strange" function that is y =
> x-1.09-2.7217*log(1+(x/2.7217));
>     When I ask to fzero with a positive initial numbre, let X0= 5, the
> answer is correct, it is 3.2106, but if I give an negative initial point
>
> (-1) the answer is -1.7701 That is not correct, and more if I call  it
> with -5 tyhe answer is -3.2701, and finally if I call it with -51the
> aswer is correct.
>     Could somebody explain to me this behavior ??
>
>     Thanks.
>
> Diego
>
>
>
>
>
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