clear all;close all;clc

xx=-1:0.01:3;
f=inline('x.^2'); % definition de la fonction, ici la fonction carre...
a=1; % tangente au point d abscisse a

figure(1);clf;

% Bornes des axes
minx=-1;maxx=4;
miny=-1;maxy=8;

cpt=0;
H=[1.5:-0.05:0.05,0.05:0.01:0.01,0.001,0.0001];
for h=H
   figure(1);clf;
   cpt=cpt+1;
   alpha=(f(a+h)-f(a))/h;
   b=f(a)-a*alpha;
   zz=alpha*xx+b;

   pp=plot(xx,f(xx),'-r',xx,zz,'-b');
   axis([minx maxx miny maxy]);
   
   hold on;

   % Les traits de construction
   plot(a,minx:0.1:f(a),'--k')
   plot(0:0.05:a,f(a),'--k')
   plot(a+h,minx:0.1:f(a+h),'--k')
   plot(0:0.05:a+h,f(a+h),'--k')
   
   % Les axes du repere
   arrowline([minx maxx-0.5],[0 0],'arrowsize', 100,'color','k');
   arrowline([0 0],[miny maxy-2],'arrowsize', 100,'color','k');

   % Texte sur la figure
   text(a-0.2,f(a)+0.2,'A','fontsize',20);
   text(a+h-0.2,f(a+h)+0.2,'M','fontsize',20);

   mytexstr = ['$\frac{f(a+h) \mbox{-} f(a)}{h}=$',num2str(alpha)];
    tt = text('string',mytexstr,...
             'interpreter','latex',...
             'fontsize',30,...
             'units','norm',...
             'pos',[0 0.9]);


   arrowline([a a+h],[miny+0.2 miny+0.2],'arrowsize', 100,'color','k');
   texth=['h=',num2str(h)];
   text('string',texth,'fontsize',10,'pos',[1.1 -0.6]);

   textfah=['$f(a+h)=$',num2str(f(a+h))];
   text('string',textfah,...
        'interpreter','latex',...
        'fontsize',12,...
        'pos',[-1 f(a+h)]);

   textfah=['$f(a)=$',num2str(f(a))];
    text('string',textfah,...
        'interpreter','latex',...
        'fontsize',12,...
        'pos',[-0.7 f(a)]);


   MM(cpt)=getframe;
   pause(0.001)
end

%% Enregistrer le film au format avi: 
% movie2avi(MM,filename.avi);
%
%% Conversion en gif anime (utilisant la commande unix 'convert'):
% convert filename.avi filename.gif