Why we differentiate in the gradient descent

#1

I am not able to understand why we differentiate in gradient descent.

#2

hi @Deepanshu_garg
consider gradient descent as slope of the line we are regressing on.
now to know the nature of the line slope i.e. the slope in decreasing or increasing we differentiate the gradient descent , this gives us a possitive or negative quantatity which tell the direction of the minima