$f in L_1([0,1],m)$ such that $int_0^1 f sin (n^2x) dm= 1$
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I have the space of $mathbb{K}$-valued integrable functions with respect to a Lebesgue measure $m$ and I need to find a function $f$ such that $int_0^1 |f| dm=1$ and $int_0^1 f sin(n^2x) dm=1 $, $n geq 2, n in mathbb{N}$. I was thinking to take a continuous function so it's Riemann integrable on $[0,1]$ and then I can "forget" the Lebesgue measure, but I don't know if it's a good idea.
functional-analysis lebesgue-integral lebesgue-measure
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show 3 more comments
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I have the space of $mathbb{K}$-valued integrable functions with respect to a Lebesgue measure $m$ and I need to find a function $f$ such that $int_0^1 |f| dm=1$ and $int_0^1 f sin(n^2x) dm=1 $, $n geq 2, n in mathbb{N}$. I was thinking to take a continuous function so it's Riemann integrable on $[0,1]$ and then I can "forget" the Lebesgue measure, but I don't know if it's a good idea.
functional-analysis lebesgue-integral lebesgue-measure
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What is $mathbb K$?
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– Umberto P.
Dec 16 '18 at 13:49
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What is the purpose of the cancelling $n$s? It looks like you want a function satisfying $int_0^1 f(x) sin(n^2 x) , dm(x) = 1$ for all $n$.
$endgroup$
– Umberto P.
Dec 16 '18 at 13:50
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A field, can be $mathbb{R}$ or $mathbb{C}$
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– user289143
Dec 16 '18 at 13:50
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No, that integral should be $n$, not $1$
$endgroup$
– user289143
Dec 16 '18 at 13:53
$begingroup$
What is the $n$ in between $f$ and $sin$ in the integral then?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:54
|
show 3 more comments
$begingroup$
I have the space of $mathbb{K}$-valued integrable functions with respect to a Lebesgue measure $m$ and I need to find a function $f$ such that $int_0^1 |f| dm=1$ and $int_0^1 f sin(n^2x) dm=1 $, $n geq 2, n in mathbb{N}$. I was thinking to take a continuous function so it's Riemann integrable on $[0,1]$ and then I can "forget" the Lebesgue measure, but I don't know if it's a good idea.
functional-analysis lebesgue-integral lebesgue-measure
$endgroup$
I have the space of $mathbb{K}$-valued integrable functions with respect to a Lebesgue measure $m$ and I need to find a function $f$ such that $int_0^1 |f| dm=1$ and $int_0^1 f sin(n^2x) dm=1 $, $n geq 2, n in mathbb{N}$. I was thinking to take a continuous function so it's Riemann integrable on $[0,1]$ and then I can "forget" the Lebesgue measure, but I don't know if it's a good idea.
functional-analysis lebesgue-integral lebesgue-measure
functional-analysis lebesgue-integral lebesgue-measure
edited Dec 16 '18 at 13:58
user289143
asked Dec 16 '18 at 13:43
user289143user289143
903313
903313
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What is $mathbb K$?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:49
$begingroup$
What is the purpose of the cancelling $n$s? It looks like you want a function satisfying $int_0^1 f(x) sin(n^2 x) , dm(x) = 1$ for all $n$.
$endgroup$
– Umberto P.
Dec 16 '18 at 13:50
$begingroup$
A field, can be $mathbb{R}$ or $mathbb{C}$
$endgroup$
– user289143
Dec 16 '18 at 13:50
$begingroup$
No, that integral should be $n$, not $1$
$endgroup$
– user289143
Dec 16 '18 at 13:53
$begingroup$
What is the $n$ in between $f$ and $sin$ in the integral then?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:54
|
show 3 more comments
$begingroup$
What is $mathbb K$?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:49
$begingroup$
What is the purpose of the cancelling $n$s? It looks like you want a function satisfying $int_0^1 f(x) sin(n^2 x) , dm(x) = 1$ for all $n$.
$endgroup$
– Umberto P.
Dec 16 '18 at 13:50
$begingroup$
A field, can be $mathbb{R}$ or $mathbb{C}$
$endgroup$
– user289143
Dec 16 '18 at 13:50
$begingroup$
No, that integral should be $n$, not $1$
$endgroup$
– user289143
Dec 16 '18 at 13:53
$begingroup$
What is the $n$ in between $f$ and $sin$ in the integral then?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:54
$begingroup$
What is $mathbb K$?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:49
$begingroup$
What is $mathbb K$?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:49
$begingroup$
What is the purpose of the cancelling $n$s? It looks like you want a function satisfying $int_0^1 f(x) sin(n^2 x) , dm(x) = 1$ for all $n$.
$endgroup$
– Umberto P.
Dec 16 '18 at 13:50
$begingroup$
What is the purpose of the cancelling $n$s? It looks like you want a function satisfying $int_0^1 f(x) sin(n^2 x) , dm(x) = 1$ for all $n$.
$endgroup$
– Umberto P.
Dec 16 '18 at 13:50
$begingroup$
A field, can be $mathbb{R}$ or $mathbb{C}$
$endgroup$
– user289143
Dec 16 '18 at 13:50
$begingroup$
A field, can be $mathbb{R}$ or $mathbb{C}$
$endgroup$
– user289143
Dec 16 '18 at 13:50
$begingroup$
No, that integral should be $n$, not $1$
$endgroup$
– user289143
Dec 16 '18 at 13:53
$begingroup$
No, that integral should be $n$, not $1$
$endgroup$
– user289143
Dec 16 '18 at 13:53
$begingroup$
What is the $n$ in between $f$ and $sin$ in the integral then?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:54
$begingroup$
What is the $n$ in between $f$ and $sin$ in the integral then?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:54
|
show 3 more comments
1 Answer
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$begingroup$
You won't find such a function.
If $f in L^1[0,1]$ the Riemann-Lebesgue Lemma tells you that $$lim_{n to infty} int_0^1 f(x) sin(nx) , dx = 0.$$
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$begingroup$
So, how can I show part $a)$ of this question? math.stackexchange.com/questions/3035444/…
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– user289143
Dec 16 '18 at 14:18
1
$begingroup$
Comments aren't the place for new questions; perhaps you should post that as a question.
$endgroup$
– Umberto P.
Dec 16 '18 at 16:32
add a comment |
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1 Answer
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1 Answer
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$begingroup$
You won't find such a function.
If $f in L^1[0,1]$ the Riemann-Lebesgue Lemma tells you that $$lim_{n to infty} int_0^1 f(x) sin(nx) , dx = 0.$$
$endgroup$
$begingroup$
So, how can I show part $a)$ of this question? math.stackexchange.com/questions/3035444/…
$endgroup$
– user289143
Dec 16 '18 at 14:18
1
$begingroup$
Comments aren't the place for new questions; perhaps you should post that as a question.
$endgroup$
– Umberto P.
Dec 16 '18 at 16:32
add a comment |
$begingroup$
You won't find such a function.
If $f in L^1[0,1]$ the Riemann-Lebesgue Lemma tells you that $$lim_{n to infty} int_0^1 f(x) sin(nx) , dx = 0.$$
$endgroup$
$begingroup$
So, how can I show part $a)$ of this question? math.stackexchange.com/questions/3035444/…
$endgroup$
– user289143
Dec 16 '18 at 14:18
1
$begingroup$
Comments aren't the place for new questions; perhaps you should post that as a question.
$endgroup$
– Umberto P.
Dec 16 '18 at 16:32
add a comment |
$begingroup$
You won't find such a function.
If $f in L^1[0,1]$ the Riemann-Lebesgue Lemma tells you that $$lim_{n to infty} int_0^1 f(x) sin(nx) , dx = 0.$$
$endgroup$
You won't find such a function.
If $f in L^1[0,1]$ the Riemann-Lebesgue Lemma tells you that $$lim_{n to infty} int_0^1 f(x) sin(nx) , dx = 0.$$
answered Dec 16 '18 at 14:00
Umberto P.Umberto P.
39.5k13166
39.5k13166
$begingroup$
So, how can I show part $a)$ of this question? math.stackexchange.com/questions/3035444/…
$endgroup$
– user289143
Dec 16 '18 at 14:18
1
$begingroup$
Comments aren't the place for new questions; perhaps you should post that as a question.
$endgroup$
– Umberto P.
Dec 16 '18 at 16:32
add a comment |
$begingroup$
So, how can I show part $a)$ of this question? math.stackexchange.com/questions/3035444/…
$endgroup$
– user289143
Dec 16 '18 at 14:18
1
$begingroup$
Comments aren't the place for new questions; perhaps you should post that as a question.
$endgroup$
– Umberto P.
Dec 16 '18 at 16:32
$begingroup$
So, how can I show part $a)$ of this question? math.stackexchange.com/questions/3035444/…
$endgroup$
– user289143
Dec 16 '18 at 14:18
$begingroup$
So, how can I show part $a)$ of this question? math.stackexchange.com/questions/3035444/…
$endgroup$
– user289143
Dec 16 '18 at 14:18
1
1
$begingroup$
Comments aren't the place for new questions; perhaps you should post that as a question.
$endgroup$
– Umberto P.
Dec 16 '18 at 16:32
$begingroup$
Comments aren't the place for new questions; perhaps you should post that as a question.
$endgroup$
– Umberto P.
Dec 16 '18 at 16:32
add a comment |
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$begingroup$
What is $mathbb K$?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:49
$begingroup$
What is the purpose of the cancelling $n$s? It looks like you want a function satisfying $int_0^1 f(x) sin(n^2 x) , dm(x) = 1$ for all $n$.
$endgroup$
– Umberto P.
Dec 16 '18 at 13:50
$begingroup$
A field, can be $mathbb{R}$ or $mathbb{C}$
$endgroup$
– user289143
Dec 16 '18 at 13:50
$begingroup$
No, that integral should be $n$, not $1$
$endgroup$
– user289143
Dec 16 '18 at 13:53
$begingroup$
What is the $n$ in between $f$ and $sin$ in the integral then?
$endgroup$
– Umberto P.
Dec 16 '18 at 13:54