I am trying to self-taught myself on Calculus for machine learning and read the book by Spivak. But it is too rigorous and need a lot of time to finish it.
As far as I am concerned, Calculus is only used for optimization in machine learning.
I am seeking some good calculus resources especially apt for machine learning research but less rigorous than Spivak.
Edited: After some research, I plan on going through MIT OpenCourseWare on single, multivariable calculus and differential equations. What book should I read to study calculus along watching these lectures?