Backpropagation calculus | Deep learning, chapter 4

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This one is a bit more symbol heavy, and that's actually the point. The goal here is to represent in somewhat more formal terms the intuition for how backpropagation works in part 3 of the series, hopefully providing some connection between that video and other texts/code that you come across later.

For more on backpropagation:
http://neuralnetworksanddeeplearning.com/chap2.html
https://github.com/mnielsen/neural-networks-and-deep-learning
http://colah.github.io/posts/2015-08-Backprop/

Music by Vincent Rubinetti:
https://vincerubinetti.bandcamp.com/album/the-music-of-3blue1brown

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