# Sigmoid Function

As in the last article we were discussing Perceptron. Now we will discuss the Sigmoid Activation Function. As the name represents its shape will be somewhere similar to sigma σ.

The above-mentioned figure is the graph of the sigmoid activation function. It provides the output from 0 to 1. The sigmoid activation function can be described by the following expression

First let’s assume that we put three values (0, +∞, -∞) turn by turn in the above-mentioned expression. First, let’s put 0 then the expression will become

After putting the value 0 we got the output of sigmoid function as 0.5. Now let’s put the value of -∞ in the expression of the sigmoid function

Therefore when we put the value of x as-, the output will be 0 as shown in the graph above. Now let’s put the value of + in the sigmoid function

Here comes the output when we put the value of x = + which can also be seen in the graph above. We will come towards the derivation of the sigmoid function in the next article.