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#1 Re: Help Me ! » solve system of equations » 2010-08-03 03:50:56

abotaha

bobbym

Thanks too much, you are very helpful.

Cheers,

abotaha

#2 Re: Help Me ! » solve system of equations » 2010-08-03 00:57:58

abotaha

hi bobbym,
thanks foo the help.
you mentioned that there are others solution.
could you please provide me the other, because z=0 is not a good solution in my model.
Moreover, the complex values are also not a good solution. since my model is only for real values.

#3 Help Me ! » solve system of equations » 2010-08-02 23:15:19

abotaha
Replies: 5

Hi guys,
this time i have more complicated nonlinear system equations:

It is system of 3 equations:




where A,B,C,D, and E  are constant.

Any suggestion to solve this system.

#4 Re: Help Me ! » system of nonlinear equation » 2010-07-23 09:23:44

abotaha

oh, thanks a lot
you are amazing.
i'll consider these solution and i think to find root for y i have to substitute x value in one of the equation  in post #1.

#5 Re: Help Me ! » system of nonlinear equation » 2010-07-23 08:34:39

abotaha

It could be a good idea let me try and see if there is another method.

Thanks

#6 Re: Help Me ! » system of nonlinear equation » 2010-07-23 08:18:52

abotaha

Thanks for the answer. it helps a lot and i tried to solved it using cubic formula. I searched for the cubic formula  (http://en.wikipedia.org/wiki/Cubic_formula#General_formula_of_roots). I found that there are some restriction (limitation or may say conditions) that gives different solution which I really did not understand it.
could you explain to me little bit please or any suggestion about solution using cubic formula.

#7 Help Me ! » system of nonlinear equation » 2010-07-22 22:11:16

abotaha
Replies: 10

Hello guys,

I am not good in advance mathematics.
I have system of nonlinear equation and I want to solve it analytically, but I face some difficulties.
The system is :


where:

and
are constants.

any suggestion and help would be appreciated.touched

#8 Re: Help Me ! » exponential integral » 2010-07-20 22:32:02

abotaha

Hi Bobbym,
thanks for this long explanation.
based on what i understood and i realized that it is better to use the solution that you suggested (post #4).

It is really helps a lot and i noticed that especially after your explanation.

thanks again.

abotaha.

#9 Re: Help Me ! » exponential integral » 2010-07-20 07:49:52

abotaha
bobbym wrote:

Hi abotaha;

Yes, I can translate it to 0, infinity. But c isn't even in the RHS.

My confusion stems from the fact that every time I get close to some  solution, you steer the problem in a new direction. I love looking at new ideas but having 3 different incomplete answers is only going to result in never getting an answer. I thought we were making headway with post #4. Let's try to finish one method before we move on to another one. We still don't klnow whether any of these methods are going to get the right answers. Also restructuring in terms of the gamma function is no easier than in terms of the error function. Both are tabulated functions and we can worry about them at the end. So, what one do you like?

Sorry for multi and different way of expressing the questions. I also try to time after time to simplify the problem and that way i am looking for many way in order to solve the integral in general ( analytically) without special case.
post #4 was a good solution, however i do not like to user erf function because it does not support an exact solution of my work.
In this case it is better to include gamma function as a solving tool.

if you could please help me with the gamma function, since i found a way  to deal with the boundaries integral like what i have, it is incomplete gamma function:

where

;

This is only work when n is an integer, however, this is not the case that i am considering since n is not integer in my problem.

Any suggestion please.

#10 Re: Help Me ! » exponential integral » 2010-07-19 22:13:30

abotaha

Hi guys,

The above integrals can be expressed in terms of the Euler gamma function:

and suppose

then


Then, use the rules:


the problem now is that the boundaries of the integral after some transformation steps are changed such that start from constant to infinity as:

so when i expressed the last integral in terms of the Euler gamma function I got:

observe the lower integral boundary is constant (c).
is there any transformation to make the low boundary zero in order to apply Gamma function formula, or is there any method to deal with this case?

#11 Re: Help Me ! » exponential integral » 2010-07-19 07:20:18

abotaha

It is nice to have this solution. I wonder if there is any way to avoid erf function.

#12 Re: Help Me ! » exponential integral » 2010-07-19 05:50:05

abotaha

Thanks bobbym for the response.
I have did the following simplification and the real bound value of the integration is from 0 to infinity:


and I separate that into three integrals:

Right now the integration seems to be simply, but it is still not easy for me to do it.
I need help please .

#13 Help Me ! » exponential integral » 2010-07-18 23:24:31

abotaha
Replies: 13

Dear all,
I have exponential integral with polynomial. I tried to solve it but I could not.
the integral is :



I complete the square of the exponential power and it looks like:

but it is still not easy for me to solve it

Can any one help me please.

Thanks in advance.

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