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Trignometry

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10 Feb 2012 19:32:21 IST

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trigo

Mathematics

3cosx+2cos3x=cosy & 2sin+2sin3x=siny find cos2x

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jagdish singh

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11 Feb 2012 08:26:18 IST

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$\hspace{-16}\mathbf{3\cos x+2\cos 3x = \cos y.................(1)}$\\\\ $\mathbf{3\sin x+2\sin 3x = \sin y...................(2)}$\\\\ Now Squaring and Adding $\mathbf{(1)}$ and $\mathbf{(2)}$, We Get\\\\ $\mathbf{9+4+12.\cos (2x) = 1}$\\\\ $\boxed{\boxed{\mathbf{\cos (2x) = -1}}}$$

abhinav

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11 Feb 2012 13:30:08 IST

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in the question 2sinx is there

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