How to call a function, como llamar una funcion

How can I call a function with this paramethers

f=-cos(x);
 a=-1;
 b=1;
 n=20;

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function [cad,g]=biseccion(f,a,b,n)
   fa=feval(f,a);
   fb=feval(f,b);
   cad=' ';
   if fa*fb<0
       for i=1:n+1
           x=(a+b)/2;
           fx=feval(f,x);
           sal=sprintf('%5d\t%15.8f\t%15.8f\t%15.8f%20s%20s%15s\n',i-1,a,x,b,cadena(fa),cadena(fx),cadena(fa*fx));
           if fa*fx<0
               b=x;
           else
               a=x;
               fa=fx;
           end
           cad=strvcat(cad, sal );
       end
       format long
       X=x;
       i=n+2;
       x=(a+b)/2;
       error=abs((x-X)/x)*100;
       sal=sprintf('%5d\t%15.8f\t%15.8f\t%15.8f\n',i-1,a,x,b);
       cad=strvcat(cad, sal );
       g=sprintf('La solución de la ecuación es %10.8f y el error es %1.8f %% \n',X,error);
   else
       g=sprintf('Cambiar de intervalo\n');
   end
end

Im trying to call like this:

biseccion(-cos(x),-1,1,20)

Undefined function or variable 'biseccion'.

>> biseccion(-cos(x),-1,1,20)

Error: File: biseccion.mlx Line: 7 Column: 19

Function with duplicate name "biseccion" cannot be defined.

Answer 1

[Jan]

Insert the code into a file called "bissecion.m" and save it to a folder, which is included in the PATH. See:

doc addpath

Then type in the command window:

f = @(x) -cos(x);
a = -1;
b = 1;
n = 20;
biseccion(f, a, b, n)

[Ana Carla Díaz Aguirre]

Thank you!!!!