Nuprl - Proof: bij imp exists inv 1 1 1 1 1 1 1

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At: bij imp exists inv 1 1 1 1 1 1 1

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

B
4.

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

a1 = a2
5. g : B

A
6.

b:B. f(g(b)) = b
7. x : A

g(f(x)) = x

By:	BackThru 4

Generated subgoal:

1 f(g(f(x))) = f(x)
1 step

About:

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