https://www.coursera.org/learn/vector-calculus-engineers#modules
Text book: https://www.math.hkust.edu.hk/~machas/vector-calculus-for-engineers.pdf
或實體書: https://www.amazon.com/Vector-Calculus-Engineers-Mathematics/dp/B0BMJMRYBH/
Week 3 Integration and Curvilinear Coordinates