function bis = bisec(f,a,b,n)
list = [];
for k=1:n
    [a,b]
    x = (a+b)/2;
    list = [list;x];
    if f(x)==0;
        bis=x;
        break
    else if f(x)*f(a)<0
        b=x;
        else if f(x)*f(b)<0
        a=x;
            end
        end
    end
end

% error = abs(list-1);  % comparison with the exact result (in this example it's equal to 1)
% semilogy(1:n,error,'r'); % error plot
bis=x;