As for analytic geometry upstairs, it may be because of its large amount of calculation, but in the third year of high school, you will find that analytic geometry is the easiest to get up if you are asked to do the problem (except the triangle solid in front, of course). Why? Most of the topics are solving equations simultaneously ... (see the answer), and there are many technical things in the analysis. Mastering many problems can be fatal, many problem-solving ideas are typical (you can look at the difficult interpretation of Longmen Project), and there are some very useful formulas that can quickly improve your problem-solving ability.
The reason why the sequence is the most troublesome is because the limit of the sequence is the first contact with college calculus. You will find that there are many abnormal difficulties in finding the general term of the abstract sequence, and you should also examine your ability to enlarge and narrow the inequality.
As for the abstract function, it is easy to surpass the class from the past, so I really want the whole series to die.
As for the triangle, it is the conversion of several formulas and calculation skills. As long as you see the cube directly on the vector, you will know. ...
In fact, this difficulty is not relative. According to the probability distribution, the most difficult thing should be the series, but the analytic geometry in our college entrance examination was the finale, but the series was also quite abnormal (there is no "first question" in analytic geometry, and I have no concept at all)