One key equation in the first programing assignment of week 4 (“step-by-step”) is equation 10:
dA[l-1]=W[l]T.dZ[l]
I don’t understand where this equation is coming from.
(I couldn’t find it in Andrew’s slides and it’s not one of the 6 key equations mentionned in the “Backpropagation Intuition” slides (week 3)).
many thanks
Hi @Nicolas_Hirel,
Welcome to the community!
Firstly, the assignment you are talking about is Building your Deep Neural Network: Step by Step, which is from Course 1 Week 4.
But I believe you are looking at the lecture slides of C1 Week 3, which is why you are unable to find those equations.
Secondly, Andrew talks about those equations in the Week 4 lecture Forward and Backward Propagation.
Although, since Andrew wants to keep the course simple and focus more on the concepts of deep learning and not the in depth mathematics behind those concepts, around 2:55, Andrew talks about those equations, including Equation 10, but also mentions I don't want to go through the detailed derivation for this...., so this equation is just provided as it is.
If it interests you, I’d encourage you research on it on your own.
Hope this helps,
Mubsi
thank you Mubsi, you’re absolutely right, I hadn’t see the week 4 slide. (well, I had seen it a few weeks ago, but forgot that this equation was mentionned then). thanks much