3blue1brown, by Grant Sanderson, is some combination of math and entertainment, depending on your disposition. The goal is for explanations to be driven by animations and for difficult problems to be made simple with changes in perspective. Contact and FAQ: https://www.3blue1brown.com/faq
24:47
But what is a Fourier series? From heat flow to circle drawings | DE4
12:12
Cramer's rule, explained geometrically | Essence of linear algebra, chapter 12
14:41
How colliding blocks act like a beam of light...to compute pi.
12:52
Ever wondered why slicing a cone gives an ellipse? It’s wonderfully clever!
15:42
Divergence and curl: The language of Maxwell's equations, fluid flow, and more
24:45
Solving 2D equations using color, a story of winding numbers and composition
17:32
Why is pi here? And why is it squared? A geometric answer to the Basel problem
19:37
Rediscovering Euler's formula with a mug (not that Euler's formula)
13:54
What is backpropagation really doing? | Deep learning, chapter 3
21:01
Gradient descent, how neural networks learn | Deep learning, chapter 2
12:39
What does area have to do with slope? | Essence of calculus, chapter 9
20:46
Integration and the fundamental theorem of calculus | Essence of calculus, chapter 8
18:27
Limits, L'Hopital's rule, and epsilon delta definitions | Essence of calculus, chapter 7
15:34
Implicit differentiation, what's going on here? | Essence of calculus, chapter 6
13:50
What's so special about Euler's number e? | Essence of calculus, chapter 5
16:52
Visualizing the chain rule and product rule | Essence of calculus, chapter 4
18:43
Derivative formulas through geometry | Essence of calculus, chapter 3