Can a function be continuous on a composed interval?

In summary, the conversation discusses whether a function can be continuous on a composed interval, using the example of f(x)=\frac{1}{x} on the interval (-\infty,0) \cup (0,\infty). The concept of continuity in topological spaces is also mentioned, with the conclusion that the answer to the question is yes, as continuity is a local concept and the function is continuous at every point in \mathbb{R}-\{0\}.
  • #1
ronaldor9
92
1
Can a function be continuous on a composed interval? For example, if [tex]f(x)=\frac{1}{x} [/tex] then on the interval [tex] (-\infty,0) \cup (0,\infty), f(x)[/tex] is continous? Or is the function [tex]f(x)[/tex] continuous on [tex] (-\infty,0) [/tex] by itself and [tex] (0,\infty)[/tex] by itself (If you don't get what I'm trying to say reply back)?
 
Physics news on Phys.org
  • #2


If you study the general definition of continuity, using topological spaces, there is no requirement that the domain be a connected set. So in general, the answer to your question is yes.
 
  • #3


ronaldor9 said:
For example, if [tex]f(x)=\frac{1}{x} [/tex] then on the interval [tex] (-\infty,0) \cup (0,\infty), f(x)[/tex] is continous? Or is the function [tex]f(x)[/tex] continuous on [tex] (-\infty,0) [/tex] by itself and [tex] (0,\infty)[/tex] by itself?
It's the same. Continuity is a local concept: a function is continuous on some domain D if it is continuous at every point in D. Since your f is continuous at every point in [tex]\mathbb{R}-\{0\}[/tex], it is continuous on every subset [tex]D\subseteq\mathbb{R}-\{0\}[/tex], in particular on [tex]D= (-\infty,0) \cup (0,\infty)[/tex].
 
  • #4


Great question with great answers!
 

1. Can a function be continuous on a composed interval if it has a discontinuity at some point within the interval?

Yes, a function can still be continuous on a composed interval even if it has a discontinuity at some point within the interval. This is because continuity is evaluated at each point individually, so as long as the function is continuous at all other points within the interval, it can still be considered continuous on the composed interval.

2. What is the difference between pointwise continuity and uniform continuity?

Pointwise continuity refers to a function being continuous at each individual point within the interval, whereas uniform continuity refers to a function being continuous on the entire interval as a whole. In other words, for uniform continuity, the function's rate of change must not vary significantly across the entire interval, while for pointwise continuity, the function's rate of change may vary at different points within the interval.

3. How is continuity related to differentiability?

Continuity and differentiability are closely related concepts. A function must be continuous at a point in order to be differentiable at that point. This means that if a function is not continuous at a point within the interval, it cannot be differentiable at that point.

4. Can a function be continuous on a composed interval if it has a removable discontinuity at one of the endpoints?

Yes, a function can still be considered continuous on a composed interval even if it has a removable discontinuity at one of the endpoints. This is because the value of the function at the endpoint can be adjusted to make the function continuous on the entire interval. However, if the discontinuity is non-removable, then the function cannot be considered continuous on the composed interval.

5. Does a function have to be continuous on both intervals in order to be continuous on a composed interval?

No, a function can be continuous on a composed interval even if it is not continuous on both intervals. As long as the function is continuous on the points where the two intervals overlap, it can be considered continuous on the composed interval. However, if the function is not continuous on any of the points where the intervals overlap, then it cannot be considered continuous on the composed interval.

Similar threads

Replies
1
Views
908
  • Calculus
Replies
9
Views
2K
Replies
3
Views
1K
Replies
2
Views
763
Replies
3
Views
2K
  • Calculus
Replies
25
Views
1K
Replies
4
Views
2K
Replies
2
Views
1K
Replies
16
Views
2K
Back
Top