Pointwise and Uniform Convergence of x^n where 0<x<1

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SUMMARY

The discussion focuses on the pointwise and uniform convergence of the function f_n(x) = x^n for the interval 0 < x < 1. The pointwise limit is established as 0 for x in [0, 1) and 1 for x = 1. The convergence is confirmed to be pointwise due to the dependence on the chosen points in the interval, while uniform convergence is shown to be false by analyzing the supremum of the difference |f_n(x) - f(x)|, which does not tend to 0 as n approaches infinity.

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Homework Statement


Almost like the title says : Let [tex]f_n (x)=x^n[/tex] for [tex]0 \leq x \leq 1[/tex]. Find the pointwise limit of [tex]f_n[/tex] and show that the convergence is not uniform.
What happens if [tex]x \in [0,1)[/tex]?





2. The attempt at a solution
[tex]\lim _{n \to \infty} f_n = \lim _{n \to \infty} x^n = 0[/tex] if [tex]x[/tex] is strictly lesser than [tex]1[/tex] and it's worth [tex]1[/tex] if [tex]x[/tex] equals [tex]1[/tex]. (I wonder if I have to prove it via the definition of limits).
I don't have much ideas about the non uniform convergence. Checking up some wikipedia, I think that if I can show that if [tex]a_n[/tex] does not tend to [tex]0[/tex] when [tex]n[/tex] tends to [tex]\infty[/tex], I'm done. Where [tex]a_n=sup |f_n (x)-f(x)|[/tex].
I get that [tex]a_n = sup |x(x^{n-1}-1)|[/tex] but I think it's worth [tex]0[/tex], hence implying the uniform convergence of [tex]f_n[/tex]...


Answering the last question : By intuition the convergence is uniform.
 
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The convergence is pointwise because the convergence of the sequence depends on what points of x you choose. Choosing x in [0,1), x=1, and x > 1 gives you a different limit.
You can use the definition of uniform convergence here: http://en.wikipedia.org/wiki/Uniform_convergence#Definition. If you are having trouble with pointwise vs. uniform convergence, compare the position of the phrase 'for all x in S' in the two definitions.
 
VeeEight said:
The convergence is pointwise because the convergence of the sequence depends on what points of x you choose. Choosing x in [0,1), x=1, and x > 1 gives you a different limit.
You can use the definition of uniform convergence here: http://en.wikipedia.org/wiki/Uniform_convergence#Definition. If you are having trouble with pointwise vs. uniform convergence, compare the position of the phrase 'for all x in S' in the two definitions.

Ok thanks, I'll try my best.
 

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