Show integrable is uniformly continuous

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In summary, the conversation discusses the problem of proving that the function F(y) = ∫g(x)f(x,y)dx from a to b is uniformly continuous, given that f is continuous and g is integrable on the interval [a,b]. The approach of separating g(x) and f(x,y) and proving their individual continuity is shown to be unsuccessful. Instead, it is suggested to use the fact that H = [a,b]x[c,d] is a compact set, making f uniformly continuous. This can be used to show that F(y) is also continuous at y0, and since y is in the compact interval [c,d], the uniform part is not necessary.
  • #1
HF08
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H = [a,b][tex]\times[/tex][c,d] . f:H[tex]\rightarrow[/tex]R is continuous, and
g:[a,b][tex]\rightarrow[/tex]R is integrable.

Prove that
F(y) = [tex]\int[/tex]g(x)f(x,y)dx from a to b is uniformly continuous.


I initially ripped g(x) and f(x,y) apart and tried to show each was continuous. This failed.
In short, I am completely stuck. Please help me.
 
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  • #2
g(x) is only given as integrable, not necessarily continuous so that couldn't work.
 
  • #3
Hint: since H is compact, f is, in fact, uniformly continuous. Use that to show for all epsilon>0, there exists a delta>0 such that |f(x,y0)-f(x,y)|<delta for all y such that |y-y0|<delta (for all x). Use that to show that the integral F(y) is continuous at y0. Once you know it's continuous, you don't have to worry about the uniform part, since y is in [c,d], which is also compact.
 

Related to Show integrable is uniformly continuous

1. What does it mean for a function to be integrable?

Integrability is a mathematical concept that describes a function's ability to be integrated, or to have a definite integral. It means that the function has a well-defined area under its curve, which can be calculated using integration methods.

2. How is integrability related to continuity?

A function must be continuous in order to be integrable. This means that the function has no sudden jumps or breaks in its graph, and its values change gradually as the input changes. If a function is not continuous, it cannot have a definite integral.

3. What does it mean for a function to be uniformly continuous?

A function is uniformly continuous if small changes in the input result in small changes in the output, regardless of where the input is on the function's domain. This is in contrast to just being continuous, where the size of the output change may depend on the specific location of the input.

4. How do you show that a function is uniformly continuous?

To show that a function is uniformly continuous, one must prove that for any given epsilon (ε) > 0, there exists a delta (δ) > 0 such that for any two points on the function's domain that are within δ units of each other, the outputs of the function at those points are within ε units of each other.

5. Why is it important to show that a function is uniformly continuous?

Uniform continuity is important because it guarantees that the function's rate of change is consistent throughout its domain. This allows for more accurate and reliable calculations of its integral, which is useful in many areas of mathematics and science, such as in physics and engineering.

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