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Differential Calculus

Blazing goIITian

Joined:	12 Apr 2008
Post:	424

26 Aug 2009 20:17:54 IST

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459

interesting question.............. no. of sol. of | lnx | = | sin (pi)x|

None

interesting question..............no. of sol. of | lnx | = | sin (pi)x|

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Comments (13)

C!-!!NMAY

Blazing goIITian

Joined: 30 Mar 2008

Posts: 1415

26 Aug 2009 20:25:47 IST

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two soln exist

vnkt. swaroop

Blazing goIITian

Joined: 13 Jun 2008

Posts: 611

26 Aug 2009 21:46:41 IST

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from the question we can say that there can be only positive values allowed.

for x=positive integers the right hand side is always equal to "zero".so there can be only one value exist for LHS also to be equal to "zero".

Hence for x=1 both are equal.

so i am getting for only one answer i am getting the RHS and LHS to be equal.

So there is only on value.

tell me whether i am correct or not?

reply is must.

C!-!!NMAY

Blazing goIITian

Joined: 30 Mar 2008

Posts: 1415

26 Aug 2009 21:48:55 IST

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bro draw the graph u will see that |sin(pix)| cut the|ln(x)| at two point ....

zzzzz

Blazing goIITian

Joined: 12 Apr 2008

Posts: 424

26 Aug 2009 21:48:59 IST

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there are 5 sol. of this question................by graph roughly 3 are clearly visible but rest two aren't that clear!!!!!!!!!!!!

C!-!!NMAY

Blazing goIITian

Joined: 30 Mar 2008

Posts: 1415

26 Aug 2009 21:49:39 IST

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okh wait checking

C!-!!NMAY

Blazing goIITian

Joined: 30 Mar 2008

Posts: 1415

26 Aug 2009 21:53:28 IST

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i got there r five soln ...i found it by graph method,,,wait trying to post here

HeMaNt..... ThE DeViL....

Blazing goIITian

Joined: 22 Jul 2008

Posts: 654

26 Aug 2009 22:01:37 IST

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yaa five soln..

C!-!!NMAY

Blazing goIITian

Joined: 30 Mar 2008

Posts: 1415

26 Aug 2009 22:10:40 IST

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yaar really unable to post pic,,,invaid bata raha hai file type,,,,kya karun

eragon24

Blazing goIITian

Joined: 14 May 2009

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26 Aug 2009 22:13:34 IST

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C!-!!NMAY

Blazing goIITian

Joined: 30 Mar 2008

Posts: 1415

26 Aug 2009 22:14:48 IST

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yup correct one

HeMaNt..... ThE DeViL....

Blazing goIITian

Joined: 22 Jul 2008

Posts: 654

26 Aug 2009 22:16:05 IST

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yaa...

zzzzz

Blazing goIITian

Joined: 12 Apr 2008

Posts: 424

26 Aug 2009 22:50:28 IST

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dude by graphing calculator u will obviously get d ans...........but d prob is in exam we r not allowed calculators..................but thanx for posting d graph

wHaT tHe F

Blazing goIITian

Joined: 18 Aug 2009

Posts: 531

27 Aug 2009 00:59:33 IST

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Dude dis can very easily be a jee question.............bcz they havent asked the solution...they hav just asked number of solutions................... i agree that it will be very difficult to draw these graphs with gr8 accuracy soas to get point of intersection of the functions....i.e the solutions...but IIT me ye question aa chuka hai[Q] the number of solutions of lnx = sinx is [a] 1 [b] 2 [c] infinite [d] 0ans is 1 bcz there is only 1 point of intersection of the functions lnx and sinx ...............

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