Why is it Called the Chain Rule?

From a channel Lumen includes in full: Every available transcript is a structured math explanation from a channel funded by Grinnell College: theorems are stated and proved (Pizza Theorem, Art Gallery Theorem), algorithms are demonstrated (divisibility by 7, Lucas–Lehmer), and series and history are explained. A few titles carry mild hooks ("What You Don't Know About...", "Are You Using Your Umbrella Correctly?"), but the content behind them is genuine teaching. The Brilliant sponsor reads are incidental rather than a sales funnel.

A 4-minute video from Tipping Point Math's catalogue; the title names its topic.

Video by Tipping Point Math, played through YouTube's embedded player.