- #1

Norm850

- 11

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I need to prove: Suppose A and B are sets, and f and g are functions with f: A -> B and g: B -> A. If g o f = idA and f o g = idB, then f is invertible and g = f^-1.

So far I have understood why g must be the inverse of f, but I do not know how to prove it.

Thanks!