import numpy as np
import matplotlib.pyplot as plt
from IPython import display

x = np.linspace(0, 6 * np.pi, 100)
cos_values = []
sin_values = []
for i in range(len(x)):
    # add the sin and cos of x at index i to the lists
    cos_values.append(np.cos(x[i]))
    sin_values.append(np.sin(x[i]))

    # graph up until index i
    plt.plot(x[:i], cos_values[:i], label='Cos')
    plt.plot(x[:i], sin_values[:i], label='Sin')
    plt.xlabel('input')
    plt.ylabel('output')

    # lines that help with animation
    display.clear_output(wait=True)  # replace figure
    plt.pause(.01)  # wait between figures