Under normal circumstances, after learning compulsory 5, it is followed by elective 2- 1 (proposition, conic equation). Some schools may take elective courses 2-2 (with emphasis on calculus) again, and take the remaining elective courses 2-3 (permutation and combination) as elective courses 4- 1, 4-4, 4-5 in the second half of the semester, and then enter the senior three general review.