import matplotlib.pyplot as plt
import numpy as np
# generate 101 x and y values between -10 and 10
x = np.linspace(-10, 10, 101)
y = np.linspace(-10, 10, 101)
# make X and Y matrices representing x and y values of 2d plane
X, Y = np.meshgrid(x, y)
# compute z value of a point as a fun...
