'''Fourth experiment with curves, Chapter 14: circle'''

import numpy as np
import matplotlib.pyplot as plt


plt.ion()
plt.axis('equal')


x = np.zeros(54)
y = np.zeros(54)


for k in range(54):
    plt.plot([-1.3, 1.3], [0, 0], 'k', [0, 0], [-1.3, 1.3], 'k')
    plt.plot(1.3, 0, 'k>', 0, 1.3,'k^')
    plt.text(1.5, 0, 'x')
    plt.text(0, 1.5, 'y')
    t = 4*np.sqrt(2)*np.pi*(k/float(50)); 
    x[k] = np.cos(t);
    y[k] = np.sin(t);
    plt.plot(x[0:k],y[0:k],'b*')
    plt.pause(0.1)
    plt.axis('equal')
    
plt.plot([-1.3, 1.3], [0, 0], 'k', [0, 0], [-1.3, 1.3], 'k')
plt.plot(1.3, 0, 'k>', 0, 1.3,'k^')
plt.text(1.5, 0, 'x')
plt.text(0, 1.5, 'y')    
t = np.linspace(0, 2*np.pi, 500)
plt.plot(np.cos(t), np.sin(t), 'm', x,y,'b*')

plt.ioff()