    import pylab
    import numpy as np

    def draw_a_line(formula, x_range, label=''):
        x = np.array(x_range)
        y = eval(formula)
        pylab.plot(x, y, '-', label=label)

    # draw -x^2
    x = np.linspace(-5, 1.5)
    y = np.negative(np.power(x, 2))
    pylab.plot(x, y, '-k', label = r'$y = -x^2$')

    # draw two lines
    draw_a_line('2*x + 1', range(-5, 3))
    draw_a_line('(2/5)*(x + 1/5) - 1/25', range(-5, 3))

    # draw a point
    pylab.plot(-1, -1, 'bo', label = r'$y^\prime(1) = -2$')
    pylab.plot(-0.2, -1/25, 'ro', label = r'$y^\prime(-\frac{1}{2}) = -\frac{1}{25}$')

    pylab.legend(loc='lower right')
    pylab.show()

# results matching ""

# No results matching ""