Formal derivatives, the epsilon-delta definition, and why L'Hôpital's rule works. Help fund future projects: https://www.patreon.com/3blue1brown An equally valuable form of support is to simply share some of the videos. Special thanks to these supporters: http://3b1b.co/lessons/limits#thanks Home page: https://www.3blue1brown.com Timestamps 0:00 - Intro 1:17 - Formal definition of derivatives 4:52 - Epsilon delta definition 9:53 - L'Hôpital's rule 17:17 - Outro Thanks to these viewers for their contributions to translations Hebrew: Omer Tuchfeld Portuguese: rose ✨ Vietnamese: ngvutuan2811 ------------------ 3blue1brown is a channel about animating math, in all senses of the word animate. And you know the drill with YouTube, if you want to stay posted about new videos, subscribe, and click the bell to receive notifications (if you're into that). If you are new to this channel and want to see more, a good place to start is this playlist: http://3b1b.co/recommended Various social media stuffs: Website: https://www.3blue1brown.com Twitter: https://twitter.com/3Blue1Brown Patreon: https://patreon.com/3blue1brown Facebook: https://www.facebook.com/3blue1brown Reddit: https://www.reddit.com/r/3Blue1Brown