$($b$)$ We know that the loss function used for training this model consists of two parts, the first part of which is as follows:

$L_1=-\frac{1}{N}log(\frac{e^{\text{s}\text{i}\text{m}\frac{x_i,y_i}{}}}{{\displaystyle \underset{j=1}{\overset{N}{}}}{e}^{\text{s}\text{i}\text{m}\frac{x_i,y_j}{}}})$

Calculate $\frac{del{L}_1}{del{x}_i}.$ That is$,$ compute the derivative of $L_1$ with respect to $x_i,$ given that sim$(x_i,y_j)=\frac{x_i*y_j}{||x_i||||y_j||}$