Binomial Coefficient/Examples/5 from 2

Proof
From the definition of binomial coefficient:


 * $\dbinom n k = \begin{cases}

\dfrac {n!} {k! \paren {n - k}!} & : 0 \le k \le n \\ & \\ 0 & : \text { otherwise } \end{cases}$

Here we have $k = 5$ and $n = 2$.

As $k > n$:


 * $\dbinom 2 5 = 0$