第一讲深入介绍如何用弧度度量角度、在度与弧度之间转换、把角放到标准位置，并在（单位）圆上使用弧长与扇形面积公式，含示例、常见陷阱与练习。

数列与它们的极限——定义、直觉、等差/等比模型与线性递推。我们定义数列、解释极限直觉、分析四个典型示例、推导等差与等比数列（含显式公式），并逐步求解线性递推 $x_{n+1}=r x_n + d$。

Summary of equivalence, similarity and congruence of matrices, core-nilpotent decompositions, Hartwig-Spindelböck factorization, and generalized inverses with applied contexts.

Overview of Schmidt orthogonalization, elementary transformation, and Givens rotation approaches to QR decomposition.

MathJax = { tex: { inlineMath: [['$', '$']] } }; This article is also available in 简体中文, 繁體中文. This article mainly studies some properties and inequalities of the traces of antisymmetric matrices. An antisymmetric…