Nuprl - Proof: inv pair inv 1 3 1 2 1 1 1 1 1

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At: inv pair inv 1 3 1 2 1 1 1 1 1

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

fg.fg/f,g. <f,g,(

x.*),(

y.*)>)

(A ~ B)
4. (

fga.fga/f,#. #/g,a. <f,g>)

(A ~ B)

B
5. f : A

B
6. g : B

A
7. a1 :

x:A. g(f(x)) = x
8. a2 :

y:B. f(g(y)) = y

x.*,

y.*> = <a1,a2>

InvFuns(A;B;f;g)

By:

Def

Generated subgoal:

1 <x.*,y.*> = <a1,a2> ((x:A. g(f(x)) = x) & (y:B. f(g(y)) = y))
8 steps

About:

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