Let f: A --> B be a function, and suppose that

there is a function g: B --> A such that g circle f is

the identity map on the set A. Prove that f is injective.

(There is a very short proof.)

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- Nov 15th 2009, 01:21 PMbrudmanProof using functions
Let f: A --> B be a function, and suppose that

there is a function g: B --> A such that g circle f is

the identity map on the set A. Prove that f is injective.

(There is a very short proof.) - Nov 15th 2009, 01:25 PMPlato