I highly encourage you to watch the 3Blue1Brown video series on youtube, and will occasionally reference them in lecture.
This is an alternate proof to the Wallis product formula from challenge problem #81 in section 7.2 of the textbook.
The Mountain Gregor Clegane introduces Improper Integrals, from my Youtube channel, where you can also find most of my 20B lectures from last quarter.
A video series about a mechanical device for computing Fourier series, developed by famed experimental physicist Michelson (who also measured the speed of light and assisted Einstein in verifying relativity).
A most beautiful proof of the Basel problem, using light.
Not related to lecture, but cool and new nonetheless, this video uses an abstract topology theorem to prove how thieves can evenly divide a stolen necklace.
Very relevant video to the topic at hand, great for conceptual understanding and visualization.
Cool application of harmonic series