% This is a sample "m-file" for MATLAB which calls the 
% MATLAB function f1.m.
%
kmax=16;
x=1;
for k=1:kmax
    h(k)=10^(-k);
%    fprime(k)=(f1(x+h(k))-f1(x))/h(k);
    fprime(k)=(f1(x+h(k))-f1(x-h(k)))/(2*h(k));
end
loglog(h,abs(fprime-cos(1)))