x=sum(((0:100)/100).^2*1/100);
x_trapeze = sum(((0:100)/100).^2*1/100)-1/100/2;
y=1/3;
erreur=x-y;
erreur_relative=(x-y)/y
erreur_trapeze=x_trapeze-y;
erreur_relative_trapeze=(x_trapeze-y)/y