Trignometry

sikha bharadwaj's Avatar
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Joined: 5 Jan 2007
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11 Jan 2007 07:47:04 IST
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trigonometry
Engineering Entrance , JEE Main , JEE Main & Advanced , Mathematics , Trigonometry

If sin4/a+cos4/b=1/a+b, show that sin8/a3+cos8/b3=1/(a+b)3



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10904him's Avatar

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Joined: 29 Dec 2006
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11 Jan 2007 08:09:35 IST
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form a quadratic in cosA
which gives
(a+b)cos^4A-2bcos^2A+b^2/a+b =0
By Shreedharacharya's rule--
cos^2A=2b/2(a+b)= b/a+b .... (1)
sin^2A=a/A+b ..... (2)
thus we have---
In the required expression these values give (1/a+b)^3
Hence Proved
Krishna Gopal Singh's Avatar

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Joined: 29 Dec 2006
Posts: 5535
12 Jan 2007 11:20:39 IST
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Good work



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