Proving the Identity Function: Composed Functions

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SUMMARY

The discussion centers on proving that a function f is the identity function if it satisfies the condition that f composed with g equals g composed with f for all functions g. The key argument presented is that if f is not the identity function, there exists an x such that f(x) does not equal x. By selecting an appropriate function g that contradicts this assumption, the proof can be established. This logical approach confirms that f must indeed be the identity function.

PREREQUISITES
  • Understanding of function composition
  • Familiarity with identity functions in mathematics
  • Basic knowledge of logical reasoning in proofs
  • Concept of contradiction in mathematical arguments
NEXT STEPS
  • Study the properties of identity functions in various mathematical contexts
  • Explore function composition in detail, including examples
  • Learn about proof techniques, particularly proof by contradiction
  • Investigate the implications of function properties in algebra and calculus
USEFUL FOR

Mathematicians, students studying abstract algebra, and anyone interested in understanding function properties and proofs in mathematics.

andmcg
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Suppose that f composed with g equals g composed with f for all functions g. Show that f is the identity function.

I really just don't know where to start.
 
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That was probably a bad tip. I'll try to think of something better.

OK, here we go...

If f isn't the identity, there's an x such that f(x)≠x. Now choose a g that contradicts that.
 
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