This is essential knowledge you can get from a number of different places: first semester of university, any sort of 3d or image/signal processing, or just plain old wikipedia.
You could still use a deep learning framework as a black box without knowing how to differentiate a function. However, you'd have trouble following any relevant blog post / scientific paper, understanding how it works or developing any relevant new algorithm.
You could still use a deep learning framework as a black box without knowing how to differentiate a function. However, you'd have trouble following any relevant blog post / scientific paper, understanding how it works or developing any relevant new algorithm.