Hi there,

I need an example of a function f for which lim x->infinity f(x) exists, but lim x-> inifinity f '(x) doesn't.

- Nov 15th 2009, 01:24 PMdgmath[SOLVED] limit of function exists, but limit of its derivative doesn't.
Hi there,

I need an example of a function f for which lim x->infinity f(x) exists, but lim x-> inifinity f '(x) doesn't. - Nov 15th 2009, 02:39 PMtonio
- Nov 15th 2009, 02:59 PMJhevon
- Nov 15th 2009, 03:18 PMdgmath
- Nov 15th 2009, 03:21 PMJhevon
- Nov 15th 2009, 03:41 PMJose27
Sorry, wrong argument.

Edit: What about ? - Nov 15th 2009, 03:43 PMJhevon
- Nov 15th 2009, 04:03 PMredsoxfan325
does it.

Clearly, , but , which is undefined. - Nov 15th 2009, 04:06 PMJhevon
- Nov 15th 2009, 04:07 PMredsoxfan325
- Nov 15th 2009, 04:33 PMtonio
- Nov 15th 2009, 04:34 PMdgmath
umm, I might be acting stupid here, but I dont think that's quite right. because,

lim x-> inf sin(x^2)/x = (sin(x^2)/x^2) * (x^2/(x)) = lim x->inf 1 * x = infinity. Isn't that right? In that case, it wont work.

And if so, I think the actualy function that'd work is sinx/x^2 !!! because it will lead to limit 0. and derivative would be 2sinx/x - cosx which is DNE? - Nov 15th 2009, 04:40 PMJhevon
- Nov 15th 2009, 04:45 PMJhevon
- Nov 15th 2009, 04:45 PMredsoxfan325