secant.py

gistfile1.txt

def secant(f, a, b, tol=1e-9, n=100):
    fmt = "{:2} {:>13.10f} {:>13.10f} {:>13.10f}"
    p1, p2 = float(a), float(b)
    i = 1
    print fmt.format(1, p1, p2, f(p2))
    while abs(p1 - p2) > tol and i <= n:
        p1, p2 = p2, p2 - (f(p2) * (p2 - p1)) / (f(p2) - f(p1))
        i += 1
        print fmt.format(i, p1, p2, f(p2))
    return p2


def f(x):
    return x**3 + 4*x**3 - 10


if __name__ == "__main__":
    r1 = secant(f, 1, 2)
    print "root = {:.10f}".format(r1)