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Prove that 
cos 9x-cos 5x/sin17x-sin3x=-sin2x/cos10x

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User Servn
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1 Answer

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cos9x - cos5x = -2sin2x.sin7x
sin17x - sin3x = 2sin7x.cos10x
so f(x) =
(-2sin2x.sin7x)/(2sin7x.cos10x) =
(-sin2x)/(cos10x)

answered
User Chis
by
8.8k points

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