# Author: Alex Gezerlis

# Numerical Methods in Physics with Python (CUP, 2020)

from bisection import f

def secant(f,x0,x1,kmax=200,tol=1.e-8):

f0 = f(x0)

for k in range(1,kmax):

f1 = f(x1)

ratio = (x1 - x0)/(f1 - f0)

x2 = x1 - f1*ratio

xdiff = abs(x2-x1)

x0, x1 = x1, x2

f0 = f1

rowf = "{0:2d} {1:1.16f} {2:1.16f} {3:1.16f}"

print(rowf.format(k,x2,xdiff,abs(f(x2))))

if abs(xdiff/x2) < tol:

break

else:

x2 = None

return x2

if __name__ == '__main__':

root = secant(f,0.,1.7)

print(root); print("")

root = secant(f,2.,2.1)

print(root)