Chapter 2.9, Problem 9.15E

i.

To determine

To calculate: the value of $9!!$

ii.

To determine

To show whether $n!!$ is same as $\left(n!\right)!$

iii.

To determine

Writing n!! in product notation

iv.

To determine

Explain why the formula $\left(2k-1\right)!!= \frac{\left(2k\right)!}{k!*2^k}$ works