def triangle_area(a, b, c):
    """ Return the area of the triangle defined by ``[a, b, c]``, where each
    vertex contains floats ``[x, y]`` """

    return 0.5 * abs(
        a[0] * (b[1] - c[1]) +
        b[0] * (c[1] - a[1]) +
        c[0] * (a[1] - b[1])
    )