def get_line_equation_coefficients(location1, location2):
    """
    Get line equation coefficients for:
        latitude * a + longitude * b + c = 0

    This is a normal cartesian line (not spherical!)
    """
    if location1.longitude == location2.longitude:
        # Vertical line:
        return float(0), float(1), float(-location1.longitude)
    else:
        a = float(location1.latitude - location2.latitude) / (location1.longitude - location2.longitude)
        b = location1.latitude - location1.longitude * a
        return float(1), float(-a), float(-b)