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Share/Save/Bookmark Login/ Register to Bookmark Topic : "LIMIT" Started by Ricky

Ricky

#1 Posted 10:11pm 13-03-10  

LIMIT

Here goes my first question in TargetIIT :):):):):):)

Find the following limits -

1 > lim [ [frac]( n ) ![/]n[p] n[/p][/frac] ]

2 > lim [ [frac]( n - 1 ) ![/]n[p] n - 1.5[/p][/frac] ] e[p] n[/p]

In both cases n tends to infinity .
" BLACK HOLES RESULT FROM GOD DIVIDING THE UNIVERSE BY ZERO !!!!!! " ------ GALLARDO  Edited on 10:12pm 13-03-10    

subhomoy~~ATGS

#2 Posted 10:14pm 13-03-10  

Re: LIMIT

i hope [.] doesn't mean greatest integer function??????
"Every physicist thinks that he knows what a photon is...I spent my life to find out what a photon is and I still don't know it!!!"- _Einstein_    

subhomoy~~ATGS

#3 Posted 10:18pm 13-03-10  

Re: LIMIT

:)
"Every physicist thinks that he knows what a photon is...I spent my life to find out what a photon is and I still don't know it!!!"- _Einstein_    

subhomoy~~ATGS

#4 Posted 10:23pm 13-03-10  

Re: LIMIT

1) ans is 0
"Every physicist thinks that he knows what a photon is...I spent my life to find out what a photon is and I still don't know it!!!"- _Einstein_    

subhomoy~~ATGS

#5 Posted 10:26pm 13-03-10  

Re: LIMIT

[im]http://codecogs.izyba.com/gif.latex?\frac{n!}{n^{n}}=\frac{n(n-1)(n-2)(n-3)(n-4)....3.2.1}{n.n.n.n.n.....n.n.n}=\frac{n}{n}.\frac{n-1}{n}.\frac{n-2}{n}......\frac{3}{n}.\frac{2}{n}.\frac{1}{n}[/im]


lim n->∞  => 1/n->0...hence the result!![1][1]
"Every physicist thinks that he knows what a photon is...I spent my life to find out what a photon is and I still don't know it!!!"- _Einstein_    

govind

#6 Posted 10:30pm 13-03-10  

Re: LIMIT

Ans 1 [im]http://codecogs.izyba.com/gif.latex?\frac{n!}{n^{n}}%20=%20\frac{n(n-1)(n-2)...1}{n^{n}}%20=%20\frac{n^{n}{(1-\frac{1}{n})(1-\frac{2}{n})(1-\frac{3}{n})...}}{n^{n}}%20=%200..at..%20x%20-%20infinty[/im]
 Edited on 01:02am 14-03-10    

subhomoy~~ATGS

#7 Posted 10:34pm 13-03-10  

Re: LIMIT

that is clear!!the LOT tougher thing!![1][1]
"Every physicist thinks that he knows what a photon is...I spent my life to find out what a photon is and I still don't know it!!!"- _Einstein_    

subhomoy~~ATGS

#8 Posted 10:36pm 13-03-10  

Re: LIMIT

2nd one  apparently is either 0 or infinite!! not got any strong proof yet tho!![2][2]
"Every physicist thinks that he knows what a photon is...I spent my life to find out what a photon is and I still don't know it!!!"- _Einstein_    

subhomoy~~ATGS

#9 Posted 10:39pm 13-03-10  

Re: LIMIT

checking my basics!! lim   (e[p]x[/p]-1)/x = 1 right?? or is this wrng???i mean is it e[p]x-1[/p] or e[p]x[/p]-1???
                           x->0
"Every physicist thinks that he knows what a photon is...I spent my life to find out what a photon is and I still don't know it!!!"- _Einstein_    

subhomoy~~ATGS

#10 Posted 00:13am 14-03-10  

Re: LIMIT

no answer is surely 0 govind
"Every physicist thinks that he knows what a photon is...I spent my life to find out what a photon is and I still don't know it!!!"- _Einstein_    

subhomoy~~ATGS

#11 Posted 00:43am 14-03-10  

Re: LIMIT

infinite!!


[hide]still unsure tho!![/hide]
"Every physicist thinks that he knows what a photon is...I spent my life to find out what a photon is and I still don't know it!!!"- _Einstein_    

Maths Musing

#12 Posted 01:04am 14-03-10  

Re: LIMIT

Actually the answer's zero.
First is first , and the rest are no-where .    

Maths Musing

#13 Posted 01:07am 14-03-10  

Re: LIMIT

Atleast that is what I think -- havn't been able to prove yet .
First is first , and the rest are no-where .    

harsh

#14 Posted 01:34am 14-03-10  

Re: LIMIT

i think 2nd answer is 1
{but i am only 95% sure }
   

Ricky

#15 Posted 10:36am 14-03-10  

Re: LIMIT

OKKK , here is the solution ---

There is something called STIRLING'S APPROXIMATION , which states that for large enough n , we are allowed to write

n ! = n[p] n[/p] e[p] - n[/p] [sqrt]2 Π n[/sqrt]

or , [frac]( n - 1 ) ! x n[/] n[p] n[/p][/frac] e[p] n [/p] = [sqrt]2 Π [/sqrt]  x n[p] . 5[/p]

or , [frac]( n - 1 ) ![/]n[p] n - 1 . 5[/p][/frac] e[p] n[/p] = [sqrt]2 Π[/sqrt]

or , k = [sqrt]2 Π[/sqrt]  ( suppose )

Hence , lim[ss]n--> ∞ [/ss] k = [sqrt]2 Π[/sqrt]

[hide]Actually , the expression that I have written for stirlings approximation is approximately correct , and the real expression is pretty big and involves big - O notation of Gauss and many other complicated things which is again very tough to grasp at once -  but the result won't differ anyway . If you want to know more , just use WIKIPEDIA [/hide]
" BLACK HOLES RESULT FROM GOD DIVIDING THE UNIVERSE BY ZERO !!!!!! " ------ GALLARDO    

eureka123

#16 Posted 11:24am 14-03-10  

Re: LIMIT

that approx has been used a lot of times here..[1]
so dont worry [6]
   

Che

#17 Posted 6:47pm 14-03-10  

Re: LIMIT

@gallardo

first of all r u a student....?

ur ways doesnt seem ur r student becuz if i know correctly stirling approximation is neither in any olympiad topic and obviously not in jee.....so how u know abt it...?

btw how will u evaluate this using stirling approx. ;)

[im]http://codecogs.izyba.com/gif.latex?\lim_{n\to\infty}\;\;\;\left(\frac{n!\;\cdot\;n^{2007}}{2008\cdot2009\cdot2010\cdot2011\cdot2012\cdot\;\;\;\cdots\;\;\;\cdot%20(2007+n)}\right)[/im]

goodluck :)


Photobucket    

Ricky

#18 Posted 7:06pm 14-03-10  

Re: LIMIT

Rearranging , the givrn term =[frac]n ! 2007 ! n[p]2007[/p][/]( n + 2007 ) ![/frac]

=[frac]{ n[p]n[/p] n[p]2007[/p] } { 2007 ! } { [sqrt]2 pi n[/sqrt] } { e[p] - n [/p] }[/]( n + 2007 )[p]{ n + 2007 }[/p] { e[p] - n - 2007[/p] } { [sqrt] 2 pi ( n + 2007 ) [/sqrt] }[/frac]

=[frac]{ 2007 ! } { n[p] n + 2007[/p] } { .......}[/]{ ...... }[/frac] = [frac] { 2007 ! }[/] { [ n + 2007 ] / n }[p] n + 2007[/p] { e[p] - n - 2007 + n [/p] } [sqrt][ n + 2007 ] / n [/sqrt][/frac]

=[frac]{ 2007 ! }[/]{ 1 + [ 2007 / n ] } [p]n + 2007[/p] { e [p]- 2007[/p] } { [sqrt] 1 + [ 2007 / n ][/sqrt] }[/frac]

= [frac]2007 ![/]e [p]- 2007[/p] e [p]2007[/p][/frac] = 2007 ! , after putting the limit .
" BLACK HOLES RESULT FROM GOD DIVIDING THE UNIVERSE BY ZERO !!!!!! " ------ GALLARDO  Edited on 7:11pm 14-03-10    

Che

#19 Posted 7:17pm 14-03-10  

Re: LIMIT

yup...tahts correct...

so u know much of higher real analysis....

gr8 :)
Photobucket  Edited on 7:17pm 14-03-10    

Shankar

#20 Posted 7:28pm 14-03-10  

Re: LIMIT

I think

1-[frac](n-1)[/]n[/frac]
is not equal to ∞      as   n →∞

since,     1-[frac]∞[/]∞[/frac] = 1-1 =0

is this correct
We dont shine in our life inspite of our hardwork, mainly bcoz we NEGLECT EVERY LITTLE THING.    

Maths Musing

#21 Posted 01:08am 15-03-10  

Re: LIMIT

WOWWWW !!!!!! How did Gallardo do the generalisation , i mean the question ?????? When I fist saw the qs, , I was left completely dumbstruck !!!

Gallardo bhai , KUDOSSSSS
First is first , and the rest are no-where .    

Maths Musing

#22 Posted 01:10am 15-03-10  

Re: LIMIT

STIRLINGS APPROXIMATION -- pretty interesting thing though :o :o !!
First is first , and the rest are no-where .    
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