import math def mytf(s): return 12/(s*(s+4)*(s+5)) def angle(c): realpart = mytf(c).real imagpart = mytf(c).imag return math.degrees(math.atan2(imagpart,realpart)) guess = .5j while 180-math.fabs(angle(guess)) > .5: guess = guess + .1j realpart = mytf(guess).real imagpart = mytf(guess).imag print "Real part:",realpart,"and","Imag part:",imagpart print "Guess:",guess, "Angle:",math.fabs(angle(guess))