Newton-Raphson interpolation with model

Hello! I have a problem with Newton-Raphsons method interpolating with my model Acosh(Bx) + C. I need to find A, B and C using Newton Raphson but i'm just confused with the setup of the matrices. Here's the code:

   Guess = [1,1,1];
 A=Guess(1);
 B=Guess(2);
 C=Guess(3);
 x=1;
 i=1; % counter
 du=1; % to get inside loop

 while abs(du) > 1e-01
 A=Guess(1);
 B=Guess(2);
 C=Guess(3);  

 F1 = A*cosh(B*x) + C;
 F2 = A*cosh(B*x) + C;
 F3 = A*cosh(B*x) + C;
 Fm1 = [F1 F2 F3]';

 J1 = cosh(B*x);                 %d/dA
 J2 = A*x*sinh(B*x);       %d/dB
 J3 = 1;                                  %d/dC
 Jacobi = [J1 J2 J3]';

 du = Jacobi\Fm1;

 Guess = Guess-du;
 i= i+1
 end

Any info is appreciated. :)

[Torsten]

You need at least three points (xi,yi) of the function

y = A*cosh(B*x)+ C

to estimate A, B and C.