function x3 = regula_falsi(f, x1, x2)
% x = regula_falsi(f, x1, x2) where f is the function
% whose root is sought and x1....

f1 = f(x1);
f2 = f(x2);

for i=1:10
    % x1 and x2 bracket the root
    x3 = (f2*x1 - f1*x2) / (f2-f1);
    disp([x1 x2 x3 x2-x1])
    f3 = f(x3);

    if (f1*f3 > 0)
        f1 = f3;
        x1 = x3;
    else
        f2 = f3;
        x2 = x3;
    end
end