全英文美国大一 Calculus I 系列课。按主流 section 顺序推进,每集对齐一节课本 session:讲清定义与定理条件,再完整板书典型例题与易错点。
Differentiation Rules: Power, Product, and Quotient
The Derivative: From Secant Slopes to Instantaneous Change
Limits and Continuity: How to Read, Compute, and Test Them