[tex]cos20°cos100°+cos100°cos140°-cos140°cos200°=\frac{-3}{4}[tex]

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- Jul 6th 2009, 07:04 AMmatsci0000Trigonomertric identities
[tex]cos20°cos100°+cos100°cos140°-cos140°cos200°=\frac{-3}{4}[tex]

- Jul 6th 2009, 07:24 AMmalaygoel

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Now, see are the roots of equation

see thread: http://www.mathhelpforum.com/math-he...trigo-sum.html

hence,

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