Why is the factorial of 0 equal to 1?

Question

Wouldn’t this also mean that 1!=0!, why is this true?

In: 383

Answer 1

There is an **excellent** video by Eddie Woo on youtube, I don’t know if I can link it but I highly recommend you go watch it. However, the proof basically boils down to:

1! = 1

2! = 2

3! = 6

4! = 24

Find the pattern. To get from 4! to 3!, divide by 4. From 3! to 2!, divide by 3. From 2! to 1!, divide by 2. What will be the next answer? Divide it by 1. 0! = 1. It fits the pattern in our made up language of mathematics.