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Trignometry

Blazing goIITian

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27 May 2008 15:46:53 IST

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549

confused tricky ques DCE m-t

None

The set of values of x for which

$\frac{tan3x - tan2x}{1+ tan3xtan2x} = 1$

1) $\phi$ 2) $\frac{\pi}{4}$

3) $n\pi + \frac{\pi}{4} , n=1,2,3....$

4) $2n\pi + \frac{\pi}{4}, n = 1,2,3,....$

shouldnt the answer be option 3) but the answer in the key is given as 1)

plz explain

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Comments (9)

ashish banga

Blazing goIITian

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27 May 2008 16:04:05 IST

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sriram

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27 May 2008 16:05:26 IST

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ur key is wrong no doubt about it .......

Gaurav |spideyunlimited| Ragtah

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Joined: 16 Dec 2006

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27 May 2008 16:09:07 IST

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because in the denominator due to tan2x u will get infinity....
its not defined.. answer is nullset

S k

Blazing goIITian

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27 May 2008 16:14:25 IST

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@spideyunlimited

numerator is also infinity...limit will be ( -1 / tan3x) = 1

correct choice.... (3)

Priyesh

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27 May 2008 16:15:10 IST

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no the key cant be wrong as this question has come 2 times in two different tests and ans is given as 1)

(@ashish banga u might be having the key as u also gave the test)

Decoder

Blazing goIITian

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27 May 2008 16:15:49 IST

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ans ..is 1)...

surely...do u have x=pi/4...in the domain of tan2x function...

Decoder

Blazing goIITian

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27 May 2008 16:17:12 IST

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no limits application ..or watever...tan2x at x=pi/4..

doen't exist..

ankit aggarwal

Blazing goIITian

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28 May 2008 18:42:45 IST

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yes answer is (1) i.e phi. because after getting tanx=1 i.e. x=pie/4

if we place this value in eq. it is not satisfying it.

therefore no value of x.

aditi garg

Scorching goIITian

Joined: 2 Nov 2007

Posts: 288

28 May 2008 18:44:08 IST

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yep correct ans is 1

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