What is hiding under dy/ds?

Question

Neural networks

Here, under the beta i (layer), dE / dyi * dyi / dsi is hidden. But I wanted to clarify from the picture, in order to calculate dyi / dsi, you need to find its derivative, (in this case, the activation function of the sigmoid sigm (s)) and simply substitute this si into the derivative of the sigmoid. so we find this number dyi/dsi? and more specifically, this number will be equal to dyi / dsi = simg (s) * (1-sigm (s))