Question

Why o! =1 ???? Don't give me the answer by convention...

Answer 1

$\large{\red{\sf{Hey\:There!!!}}}$

Proof for: 0! = 1 :---

We know that,

$1! = 1!\\ 1\: \: \: \: \: = 1(0!)........ [n! = n(n-1)!] \\ 1\: \: \: \: \: = 0!$

Therefore, 0! = 1