Nuprl - Proof: bij imp exists inv 1 1

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At: bij imp exists inv 1 1

1. A : Type
2. B : Type
3. f : A

B
4.

a1,a2:A. f(a1) = f(a2)

a1 = a2
5.

b:B.

a:A. f(a) = b

g:(B

A). InvFuns(A; B; f; g)

By:	(FwdThru (Thm* Q:(ABProp). (x:A. y:B. Q(x,y)) (f:(AB). x:A. Q(x,f(x))) ([5]) THEN (Thin 5)

Generated subgoal:

1 5. f1:(BA). b:B. f(f1(b)) = b
g:(BA). InvFuns(A; B; f; g)
9 steps

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