W4_A1_Ex-8_Linear_Activation_Backward_𝑔′(𝑍[𝑙]) for relu & sigmoid

Can I find the definition of the function
sigmoid_backward and relu_backward used in this program in the function:
def linear_activation_backward(dA, cache, activation):
return dA_prev, dW, db
???

I would like to understand how the 𝑔′(𝑍[𝑙]) for relu and Signoid is calculated
Thanks a lot

@Alfiik you can check a related thread here
Keep learning!