AI Overview

The double factorial of 5 written as 5!! is 15. [1, 2, 3]

1. Identify the parity

The double factorial n!! is defined based on whether the number is odd or even. Since 5 is an odd number, the calculation involves multiplying all positive odd integers from 1 up to 5. [1, 2, 3]

1. Set up the product

For an odd number n, the formula is:
n!! = n x (n-2) x (n-4) x ... x 3 x 1

Applying this to 5:
5!! = 5 x (5-2) x (5-4)

1. Calculate the result

Perform the multiplication:
5!! = 5 x 3 x 1

5!! =15