Miller Puckette's Theory and Technique of Electronic Music. Chapter 3, Exercise 5 graphical solution.

puckette_3_5.py

import math
from pylab import *

def f(t):
  omega = 200.0 * 2 * math.pi
  return math.fmod(omega*t, 2*math.pi)/(2*math.pi)

def g(t):
  omega = 300.0 * 2 * math.pi
  return math.fmod(omega*t, 2*math.pi)/(2*math.pi)

def wrap(x):
  return math.fmod(x, 1.0)

# build dataset
data = []
rate = 1/100000.0
rng = arange(0.0, 1/100.0 + rate, rate)
for t in rng:
  data.append((f(t), g(t),
               f(t) + g(t),
               wrap(f(t) + g(t))))

# plot
plt.plot(rng, data)
plt.show()