Khan Academy (English - US curriculum)
Math by grade
Eureka Math/EngageNY
Precalculus (Eureka Math/EngageNY)
Module 1: Complex numbers and transformations
Topic C: Lessons 21-23: Transforming vectors with matrices
Intro to matrices
Intro to matrices
Take the red pill and enter the Matrix!
License: CC BY-NC-SA by Khan Academy