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Trignometry

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 Joined: 27 Dec 2006 Post: 3
27 Dec 2006 21:10:55 IST
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Engineering Entrance , JEE Main , JEE Main & Advanced , Mathematics , Trigonometry

(x tan + y cot) ( xcot +y tan) -4xycos2 2 =?

Cool goIITian

Joined: 20 Dec 2006
Posts: 31
28 Dec 2006 13:24:51 IST
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Hi (Manju)
Your question seems to be correct....
Is (x tan + y cot) ( xcot +y tan) -4xycot2 2 =?
I have the answer for this one..

Ans .  (x+y)

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Joined: 6 Dec 2006
Posts: 97
28 Dec 2006 23:32:35 IST
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hiiiiiii
are u sure abt the question,bcoz i htink that the last term should be   4xycosec2 2.
equation becomes:
x2+xy(tan2 + cot2)+y2-4xycosec22
=x2+y2+xy(sin4+cos4)/(sin2cos2) -4xycosec22
=x2+y2+xy(1-2sin2cos2)/(sin2cos2)-4xycosec22   (using the expansion for (sin2x+cos2x)2 )
=x2+y2-2xy+xy/sin2cos2-4xycosec22
=(x-y)2

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