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Trignometry

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20 Mar 2009 16:55:28 IST

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Pls.. solve very urgent... if cos^-1 a + cos-1 b + cos-1 c = pi, prove a^2 + b^2 + c^2 + 2abc =1

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Pls.. solve very urgent... if cos^-1 a + cos-1 b + cos-1 c = pi, prove a^2 + b^2 + c^2 + 2abc =1

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Lakshmi

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Joined: 4 Dec 2008

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20 Mar 2009 18:00:16 IST

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cos?x+ cos?y+ cos?z =∏

cos?x+ cos?y = ∏ - cos?z

= cos? (-z)

cos?( xy- √ (1-x^s)√(1-x^2)) = cos? (-z)

xy- √ (1-x^s)√(1-x^2)) = -z

√ (1-x^s)√(1-x^2) = xy+z

Then square

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