Factorial/Examples/1

Example of Factorial
The factorial of $1$ is $1$:
 * $1! = 1$

Proof
From the definition of factorial:
 * $n! = \displaystyle \prod_{k \mathop = 1}^n k$

where $\prod$ denotes product notation.

When $n = 1$ we have:
 * $1! = \displaystyle \prod_{k \mathop = 1}^1 k$