How to Show Zero Factorial Equals to 1?

We write 5 factorial = 5!

We find it 5! = 5×4×3×2×1

Similarly we write, 4! = 4×3×2×1

Now, we can write, 5! = 5×4!

Hence n! = n(n-1)!

Put n = 1 then,

1! = 1(1-1)!

1=0![ here 1! = 1 and 1× 0!=0!

Hence we can how that 0!=1.