Discontinuous and continuous functions

In summary, the conversation discusses the need to find a function that is continuous at 0 but discontinuous at every other point on the real number line. The proposed function is $f(x) = x$ for rational numbers and $f(x) = -x$ for irrational numbers. It is then questioned how the limit exists at a single point if the function is only continuous at that point. The conversation ends with a discussion on the definitions of limits and continuous functions.
  • #1
Carla1985
94
0
I need to find a function that is continuous at 0 but discontinuous at every other point. IV been stuck on this for hours now :( thankyou
 
Physics news on Phys.org
  • #2
Re: discontinuous and continuous functions

Carla1985 said:
I need to find a function that is continuous at 0 but discontinuous at every other point. IV been stuck on this for hours now :( thankyou

Hey Carla! ;)

How about:
$$f(x) = \left\{\begin{aligned}
x & \text{ if } x \in \mathbb Q \\
-x & \text{ if } x \in \mathbb R \backslash \mathbb Q
\end{aligned}\right.$$
 
  • #3
Carla1985 said:
I need to find a function that is continuous at 0 but discontinuous at every other point. IV been stuck on this for hours now :( thankyou

Continuous at just one point ! , then how does the limit exist ?
 
  • #4
Not a clue. I don't get it at all. The exact wording of a question, just in case iv got it wrong is: "give an example of a function defined on R which is continuous at x=0 and discontinuous at every other point of R". I like Serena, thank you :)
 
  • #5
ZaidAlyafey said:
Continuous at just one point ! , then how does the limit exist ?

Consider the definition of the limit of a function, using $(\varepsilon, \delta)$-definitions.
Combine it with the definition of a continuous function in a point.
 

FAQ: Discontinuous and continuous functions

What is the definition of a discontinuous function?

A discontinuous function is a function in which there is at least one point where the function is not defined or has a jump in its value. This means that there is a break or gap in the graph of the function, and it does not have a continuous line.

What are the types of discontinuities in a function?

The types of discontinuities in a function include removable, jump, and infinite discontinuities. A removable discontinuity occurs when there is a hole in the graph of the function, a jump discontinuity happens when the graph has a sudden jump in value, and an infinite discontinuity occurs when the function approaches positive or negative infinity at a particular point.

What is the difference between a discontinuous and continuous function?

A continuous function is one in which the graph has no breaks, gaps, or jumps and can be drawn without lifting the pencil from the paper. On the other hand, a discontinuous function has at least one point where the function is not defined or has a jump or break in its graph.

Can a function be both continuous and discontinuous?

No, a function cannot be both continuous and discontinuous. A function is either continuous or discontinuous at a particular point, but not both. However, a function can have both continuous and discontinuous parts, meaning it is continuous on some intervals and discontinuous on others.

How are discontinuous functions used in real-life applications?

Discontinuous functions are used in real-life applications to model situations where there are sudden changes or interruptions. For example, a step function can be used to model the electricity consumption in a household, where there is a sudden increase or decrease in usage at certain times of the day.

Similar threads

Replies
8
Views
2K
Replies
5
Views
2K
Replies
2
Views
889
Replies
20
Views
3K
Replies
11
Views
920
Replies
9
Views
2K
Replies
18
Views
2K
Back
Top