Return Styles: Pseud0ch, Terminal, Valhalla, NES, Geocities, Blue Moon.

Pages: 1-

Analysis, converging functions

Name: Anonymous 2007-12-09 17:33

Let f_n(x)=nx^n for 0<=x<=1 and f_n(x)=0 elsewhere.  Does f_n converge, and if so, to what function? 

Name: Anonymous 2007-12-09 19:13

It 'converges' to f(x)= inf at 1, 0 elsewhere. So, no, it doesn't, actually.

Name: Anonymous 2007-12-09 19:42

>>2
How would one go about showing that f(x)=0 for 0<=x<1? 

Name: Anonymous 2007-12-09 20:16

the power series x^n has radius of convergence (-1,1).

when n gets big the power series converges to zero.

Name: Anonymous 2007-12-10 9:22

it converges pointwise to f(x) = infinity at 1
                               = 0 elsewhere


It does not converges uniformly to this though, so it does not converges.

This can be seen obviously as for any n, there exists an x < 1 such that nx^n = 1/2   ie  nlnx = -ln2n

so x = exp(-1/n(ln(2n))


I'm not bothering to write out the definition for uniform convergence of sequences of functions, but if you can't see why that contradicts it, you're going to fail analysis anyway

Don't change these.
Name: Email:
Entire Thread Thread List