1.概念、定理、公式的分类当所给问题涉及到的数学概念、定理、公式、性质及运算性质、法则本身就是分类给出,如实数的绝对值;直线的斜率、等比数列的求和公式、对数函数的性质等,这时可考虑分类讨论. 例1 设{an)是公式为q的等比数列,Sn是它 1. Classification of Concepts, Theorems, and Formulas The mathematical concepts, theorems, formulas, properties, and nature of operations involved in the given problem, the laws themselves are given as classifications, such as the absolute value of a real number; the slope of a straight line, the summation of geometric progression Formulas, properties of logarithmic functions, etc. At this time, we can consider the classification and discussion. Example 1 Let {an) be an array of equal numbers of the formula q, where Sn is