def get_missing_coordinate(x1: float, y1: float, x2: float, angular_coefficient: float = -1.0) -> float:
    """Returns the y2 coordinate at the point (x2, y2) of a line which has an angular coefficient of
    "angular_coefficient" and passes through the point (x1, y1)."""
    linear_coefficient = y1 - (angular_coefficient * x1)
    y2 = linear_coefficient + (x2 * angular_coefficient)
    return y2