Re: from Rumen, MEXICO, petition
- To: mathgroup at smc.vnet.net
- Subject: [mg118070] Re: from Rumen, MEXICO, petition
- From: Peter <petsie at dordos.net>
- Date: Mon, 11 Apr 2011 07:07:18 -0400 (EDT)
- References: <inpeua$8ul$1@smc.vnet.net>
Am 09.04.2011 13:12, schrieb Rumen Ivanov:
> Hello,
>
> 11*Exp[-Es/135]+10.5*Exp[-Es/425]+
> 4.899*Exp[-Es/1754]+ 2.02912 = 0
> Please tell me how Mathematica can solve this equation
> for Es? With the derivatives of "Solve" it is impossible.
>
> Best
>
> Regards,
>
> Rumen
>
> Prof. Dr. Rumen Ivanov Tsonchev
> Facultad de F=EDsica
> Universidad Aut=F3noma de Zacatecas
> e-mail=B4s:
> rumen5252 at yahoo.com.mx
> rumen at fisica.uaz.edu.mx
Hello Rumen,
as has been said, there is no real solution, but to make things easier
for Mathematica, I took the Log of the Exp-sum and set it equal to
Log[-2.02912]. Then FindRoot gets an approx. solution:
In[1]:= expr=11*Exp[-Es/135]+10.5*Exp[-Es/425]+4.899*Exp[-Es/1754]+2.02912;
eqn = Log[expr - 2.02912] == Log[-2.02912];
{Es, expr} /. First @ FindRoot[eqn, {Es, 0}, MaxIterations->Infinity]
Out[3]= {298.34 -1494.67 I, 1.77636*10^-15 + 0. I}
Regards,
Peter