Hi,

In the first assignment of first week, when doing the back-propagation of the RNN, some notations didn’t feel right to me.

First, I don’t get why there is a variable dtanh. In my opinion, this notation is not consistent with the notations of the course because tanh is not a variable. Why not naming it dz, it would be more consistent both with the course and the graph right above the equations.

In addition, and this is less important, I think that it might be better to change

dtan(x)/dx = 1-tanh²(x) to dtan(x)/dx = 1-tanh(x)² because, depending on the context, tanh²(x) could be tanh(tanh(x)) or tanh(x)² while the latter is not ambiguous.

Please let me know what you think, I hope that my feedback can help to make this amazing assignment even better!