I'm not sure how to go about it.

  • Context: Graduate 
  • Thread starter Thread starter neoking77
  • Start date Start date
  • Tags Tags
    Function
Click For Summary
SUMMARY

The function f, defined as f(x) = 1 for rational numbers and f(x) = 0 for irrational numbers, is not continuous at any point on the real number line. This conclusion is based on the fact that every neighborhood around any point contains both rational and irrational numbers, preventing convergence to a single value. The discussion highlights the inherent discontinuity of f due to its definition and the density of rational and irrational numbers in the real numbers.

PREREQUISITES
  • Understanding of real analysis concepts, particularly continuity.
  • Familiarity with rational and irrational numbers.
  • Knowledge of neighborhoods in topology.
  • Basic understanding of functions and their properties.
NEXT STEPS
  • Study the definition of continuity in real analysis.
  • Explore the properties of rational and irrational numbers.
  • Learn about neighborhoods and convergence in topology.
  • Investigate other examples of discontinuous functions.
USEFUL FOR

Students of mathematics, particularly those studying real analysis, and educators looking to explain concepts of continuity and discontinuity in functions.

neoking77
Messages
30
Reaction score
0
Let f be the function that takes the value of 1 on all rational numbers, and 0 on all irrational numbers. At what points is f continuous?

Does anyone know how to do this?? I mean, there are just so many points to point out...such as square root of 2 and 10, and the list is endless...
 
Physics news on Phys.org
I'm fairly sure it's not continuous anywhere. Specifically, for any neighbourhood about any point, will contain some rationals and some irrationals, and so a sequence of decreasing neighbourhoods don't converge to any value.
 
I see! Thanks a lot!
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 36 ·
2
Replies
36
Views
7K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 11 ·
Replies
11
Views
2K