with respect to W 1 is also not directly computable we have to apply the chain rule again to evaluate this so let's apply the chain rule again we can break that second term up into with respect to now the the state Z ok and using that we can kind of back propagate all of these gradients from the output all the way back to the input that allows our error signal to really propagate from output to input and allows these gradients to be computed in practice now a lot of this is not really important or excuse me it's not as