% fixpont iteracioval x = cos(x)
% itt megint x = g(x) formaban kell
a = 0
b = 1
function y = g(x)
  y = cos(x);
endfunction
function y = dg(x)
  y = -sin(x);
endfunction
t = 0:0.05:1;
% feltetel ellenorzes: ertekkeszlet resze [0,1]-nek
plot(t,g(t),t,t*0)
% derivaltas feltetel....
plot(t,dg(t),t,t*0)
dg(1)
% hibabecsleshez
q = 0.85;
% (1-q)-val osztunk hibabecslesben > 1-hez kozeli q-val
% lassu a konvergencia
x = 0
n = 0
do
  x_regi = x;
  x = g(x)
  hiba = abs(x - x_regi)*q/(1-q)
  n = n+1;
until (hiba < 0.1)
n