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Share/Save/Bookmark Login/ Register to Bookmark Topic : "Some must see problems......" Started by Abhishek

Abhishek

#1 Posted 3:10pm 12-10-08  

Some must see problems......

Q1. L[ss]1[/ss] ≡ ax+by+c and L[ss]2[/ss] ≡ lx+my+n , where a,b,c,l,m,n are real.
L[ss]1[/ss]+λL[ss]2[/ss]=0 represent all lines passing through intersection of L[ss]1[/ss]=0 and L[ss]2[/ss]=0
(True/False)?
______________________________________________________

Q2. Lim(x→0)(sin(1/x))/(sin(1/x)) = ?

______________________________________________________

Q.3 x = (2y±(2y-1-y[p]2[/p])[p]1/2[/p] )/2 is a second degree general curve here it represents ?

______________________________________________________

Q.4 The solution of f(x)=f[p]-1[/p](x) if exists lie on ?
a) y=x
b) y=-x
c) None(Specify)

______________________________________________________
http://priyamsays.blogspot.com    

Nishant

#2 Posted 3:12pm 12-10-08  

Re: Some must see problems......

is the 2nd question

Lim(x→0){(sin(1/x))/(sin(1/x))} = ?

or {Lim(x→0)(sin(1/x))}/{Lim(x→0)(sin(1/x))}

Both will have different answers!

I think u meant the first one...

btw both are worth trying :)
-when spring comes, it melts the snow one flake at a time…    

Nishant

#3 Posted 3:16pm 12-10-08  

Re: Some must see problems......

To add to question 1 (first part)

If false, give a general form which will actually satisfy all lines criterion
-when spring comes, it melts the snow one flake at a time…    

Abhishek

#4 Posted 6:36pm 12-10-08  

Re: Some must see problems......

I think no one is trying this!
http://priyamsays.blogspot.com    

Ashish

#5 Posted 6:38pm 12-10-08  

Re: Some must see problems......

To nishant


Lim(x→0){(sin(1/x))/(sin(1/x))} = 1

or {Lim(x→0)(sin(1/x))}/{Lim(x→0)(sin(1/x))} =1 both are smae
   

Ashish

#6 Posted 6:40pm 12-10-08  

Re: Some must see problems......

i think second part is easy....

other questions i cannoth think now..

in Q1 i think it will be only that it will use all lines
   

Ashish

#7 Posted 6:49pm 12-10-08  

Re: Some must see problems......

Q4) f(f(x)) =x we have to solve...

so it can be anywhere!
   

skygirl

#8 Posted 7:01pm 12-10-08  

Re: Some must see problems......

i think the first one is true.
isnt it?
http://skygirl-tete-a-tete.blogspot.com/ [phool bankar muskurana, zindagi hai... muskurake gham bhulana, zindagi hai... jeet kar koi khush ho toh kya hua?? ... sab kuchh har kar khushiyaan manana, ZINDAGI hai... :) ]    

Nishant

#9 Posted 7:02pm 12-10-08  

Re: Some must see problems......

NO :(
-when spring comes, it melts the snow one flake at a time…    

Nishant

#10 Posted 7:03pm 12-10-08  

Re: Some must see problems......

akshat all ur answers have mistakes :(
-when spring comes, it melts the snow one flake at a time…    

voldy

#11 Posted 09:19am 13-10-08  

Re: Some must see problems......

Nishant , isn't the first one true ?

let the point of intersection be ( h , k)

L[ss]1[/ss] = ah + bk + c = 0
and L[ss]2[/ss] = lh + mk +n = 0

therefore any linear combination  i.e  L[ss]1[/ss] +λ L[ss]2[/ss] = 0 is true for all λ , as L[ss]1[/ss] and L[ss]2[/ss] are separately 0 .
behind every lie there's a truth    

Abhishek

#12 Posted 09:23am 13-10-08  

4 2nd question...

Read the def of limits...

lim(x→a)f(x)=b means as value of x approaches 'a' [i](always keeping itself in the domain of the function)[/i] f(x) approaches a fixed value 'b'.


http://priyamsays.blogspot.com    

Abhishek

#13 Posted 09:25am 13-10-08  

@Srinath...

Does that linear combination represents the parent line L[ss]2[/ss] for any value of λ.

More appropriate linear combination would be ...........
http://priyamsays.blogspot.com    

Abhishek

#14 Posted 3:54pm 13-10-08  

Re: Some must see problems......

Actually the linear combination is λ[ss]1[/ss]L[ss]1[/ss]+λ[ss]2[/ss]L[ss]2[/ss]=0
and we divide entire eqn by λ[ss]1[/ss] and write λ[ss]1[/ss]/λ[ss]2[/ss] = λ assuming λ[ss]1[/ss] is not equal to 0 thus 1 line is lost in the family.
http://priyamsays.blogspot.com    

Nishant

#15 Posted 6:04pm 13-10-08  

Re: Some must see problems......

well abhishek there u are perfectly correct...

btw ur answers will give a few repetitions...

may be this form? λL[ss]1[/ss]+(1-λ)L[ss]2[/ss]=0 {0≤λ≤1}
-when spring comes, it melts the snow one flake at a time…    

Nishant

#16 Posted 6:05pm 13-10-08  

Re: Some must see problems......

In my opinion, this is a slightly better form of ur solution.. *only slightly :)
-when spring comes, it melts the snow one flake at a time…    

Abhishek

#17 Posted 11:48pm 13-10-08  

Re: Some must see problems......

Gr8 i never took notice of that λ/1-λ captures whole R
http://priyamsays.blogspot.com    

Nishant

#18 Posted 11:50pm 13-10-08  

Re: Some must see problems......

only +ve R!

why dont we need the negative side here?
-when spring comes, it melts the snow one flake at a time…    

Abhishek

#19 Posted 00:04am 14-10-08  

Re: Some must see problems......

What a gud question i have touched!!! now i need time to think...

may be 4 same reason we need only 0-pi angle 4 line's slope.. well may be..
http://priyamsays.blogspot.com    

Nishant

#20 Posted 00:19am 14-10-08  

Re: Some must see problems......

hey hang on.. i am getting confused :D

wait give me 5 mins.. i will tell u exactly what :)
-when spring comes, it melts the snow one flake at a time…    

Abhishek

#21 Posted 00:23am 14-10-08  

Re: Some must see problems......

0 to Pi  was a guess
http://priyamsays.blogspot.com    

Nishant

#22 Posted 00:23am 14-10-08  

Re: Some must see problems......

yeah i am wrong..

it should have been -1<=λ<=1

sory :)

y? because take an example x=0, y=0

will this give the set of all lines?

no it will give lines only on +ve quadrant!

It will not generate x-y=0!
-when spring comes, it melts the snow one flake at a time…    

Nishant

#23 Posted 00:25am 14-10-08  

Re: Some must see problems......

okie.. that 0-pi was a good guess... i mean the line sweeps the whole plane

I though the same thing wud work here as well.. but it does not..

So this correction :)
-when spring comes, it melts the snow one flake at a time…    

Abhishek

#24 Posted 00:28am 14-10-08  

Re: Some must see problems......

Now here comes a complete soln of a question but lets see if others try other questions....
http://priyamsays.blogspot.com    

Nishant

#25 Posted 00:33am 14-10-08  

Re: Some must see problems......

yup.. unfortunately not too many active users on the forum...


they come.. they see.. they go :D
-when spring comes, it melts the snow one flake at a time…    

Kumar

#26 Posted 1:27pm 14-10-08  

Re: Some must see problems......

good everyone.. i like this all questions.. i will try to answer...

Q2. Lim(x→0)(sin(1/x))/(sin(1/x)) = ?

answer will be 1 . because it is lim(x-0) {1}


the other thing.
when in same question there was another case...

answer will be 1 again.
Keep Working    

Abhishek

#27 Posted 2:24pm 14-10-08  

Re: Some must see problems......

Oh no first Lim(x→0)(sin(1/x))/(sin(1/x)) , according 2 me limit should not exist as limit exists if the limit approach a fixed quantity no matter from which path we approach it but here  we can't approach 0 with path i.e. x=1/n*Pi  and a very infinetisimal  interval across zero will contain numerous points not in domain. [u]but i'm not sure......[/u]
http://priyamsays.blogspot.com    

Kumar

#28 Posted 2:24pm 14-10-08  

Re: Some must see problems......

oh.. yes i think.. indeterminate by indeterminate? right?

so be indeterminate na?
Keep Working    

Nishant

#29 Posted 2:26pm 14-10-08  

Re: Some must see problems......

yes.. priyam u are perfectly right.. my wrong :D
-when spring comes, it melts the snow one flake at a time…    

Kumar

#30 Posted 2:28pm 14-10-08  

Re: Some must see problems......

hmm.. good question.. i not think that way..

good abhishek .. i like your answer
Keep Working    

Kumar

#31 Posted 2:30pm 14-10-08  

Re: Some must see problems......

4th part is it x=y?

i think if not wrong.. it is reflection on x=y

but will this is correct answer i dont know.. my guess only
Keep Working    

Anuj

#32 Posted 6:07pm 14-10-08  

Re: Some must see problems......

last question is x=y.. this is because of reflection property of inverse functions

good discussion b/w abhishek and nishant .. i liked it and learned from it as well !
   

Nishant

#33 Posted 6:15pm 14-10-08  

Re: Some must see problems......

it is x=y..
-when spring comes, it melts the snow one flake at a time…    

Abhishek

#34 Posted 9:10pm 14-10-08  

Re: Some must see problems......

Last answer is not x=y, consider f(x)=-x+sin(x)..................
http://priyamsays.blogspot.com    

Nishant

#35 Posted 9:19pm 14-10-08  

Re: Some must see problems......

As long as inverses are functions.. they will meet at x=y

the condition for them not to meet is that the "inverse" are not functions but relations (sorry for putting this relation crap in between..)  !
-when spring comes, it melts the snow one flake at a time…    

Abhishek

#36 Posted 9:30pm 14-10-08  

Re: Some must see problems......

What about f(x)=-x+sin(x)
http://priyamsays.blogspot.com    

Kumar

#37 Posted 9:32pm 14-10-08  

Re: Some must see problems......

you two are interesting :)
Keep Working    

Nishant

#38 Posted 9:33pm 14-10-08  

Re: Some must see problems......

and for that what is the point which is not on x=y?
-when spring comes, it melts the snow one flake at a time…    

Nishant

#39 Posted 9:36pm 14-10-08  

Re: Some must see problems......

if u are not convinced...  i will try to find some good reference to support my case :)


Or try to prove this thing myself (which seems unlikely!)
-when spring comes, it melts the snow one flake at a time…    

Abhishek

#40 Posted 9:37pm 14-10-08  

Re: Some must see problems......

But if we plot graph of f(x)=-x+sin(x) and reflect it about y=x and the reflected graph and original graph intersect at many points other than y=x
http://priyamsays.blogspot.com    

Kumar

#41 Posted 9:37pm 14-10-08  

Re: Some must see problems......

hehe :)

I am reading... good god...

but i think it is reflection along x=y... so they cant meet anywhere else!
Keep Working    

Nishant

#42 Posted 9:39pm 14-10-08  

Re: Some must see problems......

hmm.. i can see where u got this from..

ok i will try to make sure i am right.. and then tell u why this is happening...

because u could have givne a simpler function

x=-y!!

their inverse will meet everywhere....

but just let me check once more...
-when spring comes, it melts the snow one flake at a time…    

Nishant

#43 Posted 9:40pm 14-10-08  

Re: Some must see problems......

and after seeing this function


x=-y.. even i have started to believe that i am wrong!
these two meet at all points.. and they seem to be invertible !
-when spring comes, it melts the snow one flake at a time…    

Kumar

#44 Posted 9:40pm 14-10-08  

Re: Some must see problems......

interesting!

i never think that way!
Keep Working    

Nishant

#45 Posted 9:50pm 14-10-08  

Re: Some must see problems......

I searched the net.. somehow i am getting 2-3 sites that say what i am saying..

But there is no denying that u are right... absolutely.

I remember my fiitjee teacher ofcourse many years back having taught this same thing :D

And he was an IIT Kanpur Gold Medalist Mathematics(Rank 1!)

So he coulnt have been wrong :D .. alas :))

This one is going in the next news letter with credits to you :)

-when spring comes, it melts the snow one flake at a time…    

Abhishek

#46 Posted 9:50pm 14-10-08  

Re: Some must see problems......

Oh, my teacher asked me this and we were blank so he gave us that example so i never thought of simpler example y=-x
http://priyamsays.blogspot.com    

Abhishek

#47 Posted 9:52pm 14-10-08  

Re: Some must see problems......

Oh my fiitjee teacher also has taught that last year.....
http://priyamsays.blogspot.com    

Abhishek

#48 Posted 9:55pm 14-10-08  

Re: Some must see problems......

Now 3 questions have lead 2 good conclusions now last question of the topic is left but an easy one...
http://priyamsays.blogspot.com    

Kumar

#49 Posted 11:32pm 14-10-08  

Re: Some must see problems......

q3-- 2 lines.. 3y-1=x and y+1=x...

is this the answers?
Keep Working    

Abhishek

#50 Posted 11:38pm 14-10-08  

Re: Some must see problems......

Check question once more.......
http://priyamsays.blogspot.com    
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