Uniform Continuity: Showing f*g Is Uniformly Continuous on Bounded X

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SUMMARY

To demonstrate that the product of two uniformly continuous functions, f and g, is uniformly continuous on a bounded set X, both functions must be uniformly continuous and bounded. The proof involves showing that the expression |f(x)g(x) - f(y)g(y)| can be made arbitrarily small by controlling |x - y| through the use of epsilon-delta definitions. The hint provided emphasizes breaking down the product into manageable parts, leveraging the uniform continuity of f and g to establish the desired result.

PREREQUISITES
  • Understanding of uniform continuity and its definition.
  • Familiarity with epsilon-delta proofs in analysis.
  • Knowledge of bounded functions and their properties.
  • Basic algebraic manipulation of inequalities involving functions.
NEXT STEPS
  • Study the formal definition of uniform continuity in detail.
  • Learn how to apply epsilon-delta arguments in proofs.
  • Explore examples of uniformly continuous functions and their products.
  • Investigate the implications of boundedness on continuity properties.
USEFUL FOR

Mathematics students, particularly those studying real analysis, educators teaching continuity concepts, and anyone interested in the properties of functions in bounded domains.

CarmineCortez
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Homework Statement


suppose f and g are uniformly continuous functions on X

and f and g are bounded on X, show f*g is uniformly continuous.


The Attempt at a Solution



I know that if they are not bounded then they may not be uniformly continuous. ie x^2
and also if only one is bounded they are not necessarily uniformly continuous.

not sure what to do if they are both bounded
 
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CarmineCortez said:

Homework Statement


suppose f and g are uniformly continuous functions on X

and f and g are bounded on X, show f*g is uniformly continuous.


The Attempt at a Solution



I know that if they are not bounded then they may not be uniformly continuous. ie x^2
and also if only one is bounded they are not necessarily uniformly continuous.
No, you don't "know" that. In fact, here, you are told that they are both uniformly continuous.

not sure what to do if they are both bounded
Are you saying you could do this if only one were bounded? Do you understand what it is you are asked to prove?
 
uniform continuity is intuitively a bit like saying the function doesn't have an infinite slope anywhere...
And if they are both bounded, is their product too bounded?
 
Get your epsilons and deltas out. You want to show |f(x)g(x)-f(y)g(y)| can be made uniformly small if |x-y| is small. Hint: |f(x)g(x)-f(y)g(y)|=|f(x)g(x)-f(x)g(y)+f(x)g(y)-f(y)g(y)|. |f(x)-f(y)| and |g(x)-g(y)| can be made small since they are uniformly continuous. Do you see why f and g need to be bounded? Use epsilons and deltas to make the meaning of 'small' precise.
 

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