In first programming assigment from week 1, there is RNN with many-to-many relation, where Tx = Ty. I fully understand backprop that is provided in notebook, but I have no idea how Loss/Cost Function at each time step t should affect parameters - Waa, Wax, Wya, ba, ba, by. At the end of timestep, we calculate da_prev as shown on a figure below:

but should not da_prev be also affected by cost function of y^(t-1) ? If so, how to calculate “true da_prev”?