[tex]cos20°cos100°+cos100°cos140°-cos140°cos200°=\frac{-3}{4}[tex]
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Originally Posted by matsci0000 [tex]cos20°cos100°+cos100°cos140°-cos140°cos200°=\frac{-3}{4}[tex] = Now, see are the roots of equation see thread: http://www.mathhelpforum.com/math-he...trigo-sum.html hence, = = = =
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