function [c,it, a, b] = my_bisect_05_05(f,a,b,tol, itmax)
%bisection method 
%stop condition: |f(c_k)|<=tol o it>itmax
it=0;
ya=f(a);yb=f(b);
if (ya*yb>0)
    disp('intervallo non adatto');
    return;
end
err=inf; 
while (err>tol & it<=itmax)
    c=(a+b)/2;
    yc=f(c);
    if (ya*yc<=0)
        b=c;
        yb=yc;
    else
        a=c;
        ya=yc;
    end
    err=abs(yc);
    it=it+1;
end



end