Unbounded and continuous almost everywhere

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In summary, an unbounded function has no finite upper or lower limit and as the input values approach infinity or negative infinity, the output values also approach infinity or negative infinity, respectively. It may still be continuous everywhere, but it may also have a finite upper or lower limit. It is possible for an unbounded function to be continuous at a specific point and have a derivative at that point, but not at all points. However, it cannot have a definite integral as it has no finite upper or lower limit, making it impossible to calculate the area under the curve.
  • #1
Ja4Coltrane
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Can anyone give me an example of a function f:[a,b]->R which is continuous almost everywhere yet unbounded?

Thanks!
 
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  • #2
The function f:[0,1]->R given by
f(x) = n if x=1/n for some positive integer n
f(x) = 0 else
 
  • #3
muchas gracias
 
  • #4
Okay how about one which isn't Riemann (improper) integrable
 
  • #5
[tex]\displaystyle\sum_{ k = 1 }^\infty k \chi_{ [ 0, \frac{ 1 }{ k^2 } ] }[/tex]
 
  • #6
Um, surely f(x)=1/x for x>0 and f(0)=0 is far simpler, and does everything needed.
 

What does it mean for a function to be unbounded?

An unbounded function is one that has no finite upper or lower limit. This means that as the input values approach infinity or negative infinity, the output values also approach infinity or negative infinity, respectively.

What is the difference between unbounded and continuous everywhere?

An unbounded function may still be continuous everywhere, meaning that it has no abrupt changes or breaks in its graph. However, a continuous everywhere function may still have a finite upper or lower limit, unlike an unbounded function.

Can an unbounded function be continuous at a specific point?

Yes, it is possible for an unbounded function to be continuous at a specific point. This means that the function is defined and has a finite value at that point, and the limit of the function at that point also exists and is equal to the finite value.

Is it possible for an unbounded function to have a derivative?

Yes, an unbounded function can have a derivative. This means that the function is differentiable at a specific point, and its derivative exists at that point. However, the function may not be differentiable at all points due to its unbounded nature.

Can an unbounded function have a definite integral?

No, an unbounded function cannot have a definite integral. This is because the definite integral is used to find the area under the curve of a function, and an unbounded function has no finite upper or lower limit, making it impossible to calculate the area under the curve.

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