0
1 else n
(n-1)! fi (recursive)
Thm* 
n:
. (n)! 
A == A 
False
Thm* A:Prop. (A) Prop
j == if i=j true ; false fi
Thm* i,j:
. i=j 
| factorial |
Def (n)! == if n=0 1 else n(n-1)! fi (recursive)
Thm* |
| not |
Def A == A False
Thm* |
| eq_int |
Def i=j == if i=j true ; false fi
Thm* |
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