Generally, it depends on the mood and serious attitude of the marking teacher. If the teacher is in a good mood and knows that your answer is right, he will give you full marks as appropriate. If it is strict, he will usually deduct 1 to 2 points. The auxiliary line is not only a reference for solving problems, but also for the marking teacher to clarify your thinking of answering questions, which helps the marking teacher to revise your test paper quickly.