Question

If g(z) is the sigmoid function, then its derivative with respect to z may be written in term of g(z) as
A) g(z)(1-g(z))
B) g(z)(1+g(z))
C) -g(z)(1+g(z))
D) g(z)(g(z)-1)

Answer 1

Solution

A) g(z)(1-g(z))

Answer 2

The correct answer is option A) g(z).(1-g(z))

The sigmoid function is defined as  

g(z) = 1/(1+e^-z)

Its derivative with respect to z is defined as

(dz(x))/(d(x)) = g(z).(1-g(z))

Sigmoid function is also known as sigmoid curve as it is mathematical function having an “S” shaped curve. Often sigmoid function shows a special case of the logistic function and hence sigmoid function is sometimes also called as logistic function.