Basic complex analysis | Imaginary and complex numbers | Precalculus | Khan Academy

From a channel Lumen includes in full: Khan Academy's main channel holds thousands of free, standards-aligned lessons across maths, science, economics and the humanities, taught step by step on a digital blackboard by Sal Khan and subject experts.

A 13-minute video from Khan Academy's catalogue; the title names its topic.

Video by Khan Academy, played through YouTube's embedded player.