[Date Index]
[Thread Index]
[Author Index]
Re: Help with findroot
*To*: mathgroup at smc.vnet.net
*Subject*: [mg9225] Re: [mg9169] Help with findroot
*From*: Hugh Walker <hwalker at hypercon.com>
*Date*: Fri, 24 Oct 1997 01:00:38 -0400
*Sender*: owner-wri-mathgroup at wolfram.com
Karl Kevala writes:
> I'm having a problem using findroot to solve an equation. Perhaps
> someone
> could shed some light on what's wrong.
>
> FindRoot[Sqrt[x/(1.2 10^ -4)]==-0.1*Tan[Sqrt[x/(1.2*10^
> -4)]],{x,0.1,0.1,2}]
>
> Mathematica 3. returns a value of -0.07 for x which is not anywhere
> close to correct.
> Further, I've tried several different starting values and min/max
> limits, but
> a negative answer is always returned. Eventually I'de like to compile
> a list
> of all the roots of the equation up to, say, x=1000, but I can't even
> get one
> right now.
>
> Thanks,
I suggest you try the following approach. First, rescale your function
so that
x/1.2 10^(-4) -> z Then find the solutions
of Sqrt[z] == -0.01 Tan[Sqrt[z]]. But the solutions of this equation
are the same as the solutions of
Sqrt[z]Sin[Sqrt[z]] == -0.01 Cos[Sqrt[z]] This
problem has none of the difficulties encountered in the previous
formulation.
Hugh Walker
Gnarly Oaks
Phone: (713) 729-3093
Prev by Date:
**Re: mathematica question**
Next by Date:
**Re: mathematica question**
Previous by thread:
**Re: Help with findroot**
Next by thread:
**Re: Re: Help with findroot**
| |