Week 4 Video: Forward and Backward Propogation


I have a quick questions around the backward propagation formula at 5:15. I would appreciate any help for me to better understand the backward propagation formula.

The formula of backward propagation differs according to the activation function right? Then what activation functions we are assuming behind this formula here?


In the general formulas for back propagation, Prof Ng just uses g^{[l]}(z) and g^{[l]'}(z) for the activation function at layer l and its derivative. Then you would substitute the particular values you get at each layer with the specific functions you have chosen.