We just said that our `logistic` function is able to always return a number enclosed within zero and one, but how does this function obtain that desirable result? First of all, let's start with the logistic function formula:

As you can see, we have a ratio between a strange term *e*^{x }and one plus the same strange term *e ^{x}*. What is that strange term? It turns out that it is the natural number

*e,*which is approximately equal to 2.7183, raised to the power of

*x*. The

*e*

^{x }term is therefore named the exponential function, since it's the function obtained raising

*e*to an exponent equal to

*x*. What is the shape of this ...