[25/04, 11:17 am] +40 726 467 157: function df=DDiffAnaly(Fun,xi)
  df(1) = (Fun(xi+2*(5/100*xi)) - 2*Fun(xi+2*(5/100*xi)) + Fun(xi)) / (5/100*xi)^2;
endfunction
[25/04, 11:17 am] +40 726 467 157: f1 = @(x)x^2-2*x;
x1 = 3
a=DDiffAnaly(f1,x1)
f2 = @(x)(x^2+sqrt(x))*cos(x)/sin(x);
x2 = 2
b=DDiffAnaly(f2,x2)