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Trignometry

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2 Apr 2008 14:53:05 IST
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Find all number pairs x,y that satisfy the given equation;
None

tan4x+tan4y+2cot2x.cot2y=3+sin2(X+Y); x,y(0,/2)


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Hari Shankar's Avatar

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Joined: 28 Feb 2007
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3 Apr 2008 10:13:36 IST
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By AM-GM Inequality
 
	an^4 x + 	an^4 y + 2 cot^2 x cot^2 y geq 4
 
with equality occurring when  \tan^4x = \tan^4y = 1
 
	ext{RHS}  = 3+sin^2(x+y) leq 4
 
with equality occurring when  \sin(x+y) = 1
 
Hence the solution is x = y = rac{pi}{4}  in  [0, rac{pi}{2}]

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3 Apr 2008 11:58:13 IST
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Thank u



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