Proving uniform convergence of a sequence of functions.
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I was wondering how to prove or disprove the following sequence of functions is uniformly convergent
$$ f(n) = frac{nt}{nt+1}, n≥1, t:[0,1] to R$$
So far I have analyzed the limits at $t=0$ and $t=1$ and believe it to be point-wise convergent, but not uniformly convergent. However, I'm not sure how to prove this.
Also, how does the above sequence vary from
$$ f(n) = frac{nt}{n+t}, n≥1, t:[0,1] to R$$
in regards to uniform convergence?
sequences-and-series convergence proof-writing
New contributor
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up vote
1
down vote
favorite
I was wondering how to prove or disprove the following sequence of functions is uniformly convergent
$$ f(n) = frac{nt}{nt+1}, n≥1, t:[0,1] to R$$
So far I have analyzed the limits at $t=0$ and $t=1$ and believe it to be point-wise convergent, but not uniformly convergent. However, I'm not sure how to prove this.
Also, how does the above sequence vary from
$$ f(n) = frac{nt}{n+t}, n≥1, t:[0,1] to R$$
in regards to uniform convergence?
sequences-and-series convergence proof-writing
New contributor
Maybe you mean $f(t)$ or $f_n(t)$, with $t in [0, 1]$ and $n in mathbb{N}$, right?
– the_candyman
6 hours ago
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up vote
1
down vote
favorite
up vote
1
down vote
favorite
I was wondering how to prove or disprove the following sequence of functions is uniformly convergent
$$ f(n) = frac{nt}{nt+1}, n≥1, t:[0,1] to R$$
So far I have analyzed the limits at $t=0$ and $t=1$ and believe it to be point-wise convergent, but not uniformly convergent. However, I'm not sure how to prove this.
Also, how does the above sequence vary from
$$ f(n) = frac{nt}{n+t}, n≥1, t:[0,1] to R$$
in regards to uniform convergence?
sequences-and-series convergence proof-writing
New contributor
I was wondering how to prove or disprove the following sequence of functions is uniformly convergent
$$ f(n) = frac{nt}{nt+1}, n≥1, t:[0,1] to R$$
So far I have analyzed the limits at $t=0$ and $t=1$ and believe it to be point-wise convergent, but not uniformly convergent. However, I'm not sure how to prove this.
Also, how does the above sequence vary from
$$ f(n) = frac{nt}{n+t}, n≥1, t:[0,1] to R$$
in regards to uniform convergence?
sequences-and-series convergence proof-writing
sequences-and-series convergence proof-writing
New contributor
New contributor
edited 4 hours ago
New contributor
asked 6 hours ago
MathGirl25
63
63
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New contributor
Maybe you mean $f(t)$ or $f_n(t)$, with $t in [0, 1]$ and $n in mathbb{N}$, right?
– the_candyman
6 hours ago
add a comment |
Maybe you mean $f(t)$ or $f_n(t)$, with $t in [0, 1]$ and $n in mathbb{N}$, right?
– the_candyman
6 hours ago
Maybe you mean $f(t)$ or $f_n(t)$, with $t in [0, 1]$ and $n in mathbb{N}$, right?
– the_candyman
6 hours ago
Maybe you mean $f(t)$ or $f_n(t)$, with $t in [0, 1]$ and $n in mathbb{N}$, right?
– the_candyman
6 hours ago
add a comment |
3 Answers
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Observe $$f_n(t)=frac{nt}{nt+1}=dfrac{t}{t+dfrac{1}{n}}tobegin{cases}0 , &t=0\1, &tneq0end{cases}$$
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2
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For $t$ fixed in $(0,1]$,
$$lim_{nto+infty}f_n(t)=1=f(t)$$
$$lim_{nto+infty}f_n(0)=0=f(0)$$
the pointwise limit $f$ is not continuous at $[0,1]$, the convergence is Not uniform since all $f_n$ are continuous at $[0,1]$.
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up vote
1
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The sequence
$$f_n(t) = frac{nt}{nt+1}$$
converges (in a point-wise sense) to:
$$f(t) = begin{cases}
0 & text{if}~t=0\
1 & text{if}~0<tleq 1
end{cases}.$$
To check uniform convergence, you need to evaluate $d_n(t) = |f_n(t) - f(t)|$:
$$d_n(t) = begin{cases}
0 & text{if}~t=0\
displaystyle frac{1}{nt+1} & text{if}~0<tleq 1
end{cases}.$$
Notice that:
$$sup_{t in [0,1]} d_n(t) = 1,$$
which does not converge to $0$ as $n$ goes to infinity. Therefore, convergence is not uniform.
add a comment |
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
Observe $$f_n(t)=frac{nt}{nt+1}=dfrac{t}{t+dfrac{1}{n}}tobegin{cases}0 , &t=0\1, &tneq0end{cases}$$
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3
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Observe $$f_n(t)=frac{nt}{nt+1}=dfrac{t}{t+dfrac{1}{n}}tobegin{cases}0 , &t=0\1, &tneq0end{cases}$$
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up vote
3
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up vote
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Observe $$f_n(t)=frac{nt}{nt+1}=dfrac{t}{t+dfrac{1}{n}}tobegin{cases}0 , &t=0\1, &tneq0end{cases}$$
Observe $$f_n(t)=frac{nt}{nt+1}=dfrac{t}{t+dfrac{1}{n}}tobegin{cases}0 , &t=0\1, &tneq0end{cases}$$
answered 6 hours ago
Yadati Kiran
1,289417
1,289417
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add a comment |
up vote
2
down vote
For $t$ fixed in $(0,1]$,
$$lim_{nto+infty}f_n(t)=1=f(t)$$
$$lim_{nto+infty}f_n(0)=0=f(0)$$
the pointwise limit $f$ is not continuous at $[0,1]$, the convergence is Not uniform since all $f_n$ are continuous at $[0,1]$.
add a comment |
up vote
2
down vote
For $t$ fixed in $(0,1]$,
$$lim_{nto+infty}f_n(t)=1=f(t)$$
$$lim_{nto+infty}f_n(0)=0=f(0)$$
the pointwise limit $f$ is not continuous at $[0,1]$, the convergence is Not uniform since all $f_n$ are continuous at $[0,1]$.
add a comment |
up vote
2
down vote
up vote
2
down vote
For $t$ fixed in $(0,1]$,
$$lim_{nto+infty}f_n(t)=1=f(t)$$
$$lim_{nto+infty}f_n(0)=0=f(0)$$
the pointwise limit $f$ is not continuous at $[0,1]$, the convergence is Not uniform since all $f_n$ are continuous at $[0,1]$.
For $t$ fixed in $(0,1]$,
$$lim_{nto+infty}f_n(t)=1=f(t)$$
$$lim_{nto+infty}f_n(0)=0=f(0)$$
the pointwise limit $f$ is not continuous at $[0,1]$, the convergence is Not uniform since all $f_n$ are continuous at $[0,1]$.
edited 5 hours ago
answered 6 hours ago
hamam_Abdallah
37.5k21634
37.5k21634
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add a comment |
up vote
1
down vote
The sequence
$$f_n(t) = frac{nt}{nt+1}$$
converges (in a point-wise sense) to:
$$f(t) = begin{cases}
0 & text{if}~t=0\
1 & text{if}~0<tleq 1
end{cases}.$$
To check uniform convergence, you need to evaluate $d_n(t) = |f_n(t) - f(t)|$:
$$d_n(t) = begin{cases}
0 & text{if}~t=0\
displaystyle frac{1}{nt+1} & text{if}~0<tleq 1
end{cases}.$$
Notice that:
$$sup_{t in [0,1]} d_n(t) = 1,$$
which does not converge to $0$ as $n$ goes to infinity. Therefore, convergence is not uniform.
add a comment |
up vote
1
down vote
The sequence
$$f_n(t) = frac{nt}{nt+1}$$
converges (in a point-wise sense) to:
$$f(t) = begin{cases}
0 & text{if}~t=0\
1 & text{if}~0<tleq 1
end{cases}.$$
To check uniform convergence, you need to evaluate $d_n(t) = |f_n(t) - f(t)|$:
$$d_n(t) = begin{cases}
0 & text{if}~t=0\
displaystyle frac{1}{nt+1} & text{if}~0<tleq 1
end{cases}.$$
Notice that:
$$sup_{t in [0,1]} d_n(t) = 1,$$
which does not converge to $0$ as $n$ goes to infinity. Therefore, convergence is not uniform.
add a comment |
up vote
1
down vote
up vote
1
down vote
The sequence
$$f_n(t) = frac{nt}{nt+1}$$
converges (in a point-wise sense) to:
$$f(t) = begin{cases}
0 & text{if}~t=0\
1 & text{if}~0<tleq 1
end{cases}.$$
To check uniform convergence, you need to evaluate $d_n(t) = |f_n(t) - f(t)|$:
$$d_n(t) = begin{cases}
0 & text{if}~t=0\
displaystyle frac{1}{nt+1} & text{if}~0<tleq 1
end{cases}.$$
Notice that:
$$sup_{t in [0,1]} d_n(t) = 1,$$
which does not converge to $0$ as $n$ goes to infinity. Therefore, convergence is not uniform.
The sequence
$$f_n(t) = frac{nt}{nt+1}$$
converges (in a point-wise sense) to:
$$f(t) = begin{cases}
0 & text{if}~t=0\
1 & text{if}~0<tleq 1
end{cases}.$$
To check uniform convergence, you need to evaluate $d_n(t) = |f_n(t) - f(t)|$:
$$d_n(t) = begin{cases}
0 & text{if}~t=0\
displaystyle frac{1}{nt+1} & text{if}~0<tleq 1
end{cases}.$$
Notice that:
$$sup_{t in [0,1]} d_n(t) = 1,$$
which does not converge to $0$ as $n$ goes to infinity. Therefore, convergence is not uniform.
answered 6 hours ago
the_candyman
8,69822044
8,69822044
add a comment |
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MathGirl25 is a new contributor. Be nice, and check out our Code of Conduct.
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Maybe you mean $f(t)$ or $f_n(t)$, with $t in [0, 1]$ and $n in mathbb{N}$, right?
– the_candyman
6 hours ago