%problem 3  erfan bayat 91109843
x0 = 4;%initial amount
x1 = 4.5;%initial amount
y = 1;
while abs(y)> 10^(-10)
    f0 = (x0) - tan(x0);
    f1 = (x1) - tan(x1);
    xk = (((x0 * f1)-(x1 * f0)) / (f1 - f0));% vatari formula
    x0 = x1;
    x1 = xk;
    y = (xk) - tan(xk);
end
vpa(xk,10)