Solving equation in Mathematica

  • Mathematica
  • Thread starter EngWiPy
  • Start date
  • #1
1,367
61
Hello,

I have the following code to find the parameters Na and Q that make the expression equals [tex]10^{-10}[/tex]:

Code:
Na =.;
Q =.;
MGF[s_, gC_] := 1/(1 - gC*s);
SNRdB = 0;
SNR = 10^(SNRdB/10);
gC = 0.5*SNR;
p = gA*gB;
A = 23;
Solve[((E^(A/2)*2^-Q)/SNR \!\(
\*UnderoverscriptBox[\(\[Sum]\), \(q = 0\), \(Q\)]\(-
\*SuperscriptBox[\(1\), \(Na + q + 1\)]\)*Binomial[Q, q]*Re[
\*FractionBox[\(MGF[\(-
\*FractionBox[\(A + \((2*Pi*I \((Na + q + 1)\))\)\), \(2\ SNR\)]\), 
          gC]\), 
FractionBox[\(A + 2*Pi*I \((Na + q + 1)\)\), \(2\ SNR\)]]]\)) == 
   10^-10, {Na, Q}]
But it doesn't work? Anyone have any idea about how solving this equation?

Thanks in advance
 

Answers and Replies

  • #2
29,956
6,353
There are not analytical solutions for all equations. Functions like Solve, Reduce, DSolve, etc. will not always be able to find a solution. In such cases you can only find numerical solutions using e.g. FindRoot.
 
  • #3
1,367
61
There are not analytical solutions for all equations. Functions like Solve, Reduce, DSolve, etc. will not always be able to find a solution. In such cases you can only find numerical solutions using e.g. FindRoot.
Thanks DaleSpam for replying,

So, you are saying that If I replace the "Solve" command by "FindRoot", I may get a result?

Regards
 
  • #4
29,956
6,353
The syntax for FindRoot is a little different than for Solve. You should use the help menu to find the new syntax and some examples.
 
  • #5
1,367
61
The syntax for FindRoot is a little different than for Solve. You should use the help menu to find the new syntax and some examples.
Ok, I will. Thanks again
 

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