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Express each of the following as the sum...

Express each of the following as the sum or difference of sines and cosines: `\ 2sin4thetasin3theta`

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`2 sin 4 theta sin 3 theta`
`because, 2 sin A sin B`
`=cos (A-B)-cos (A+B)`
`Rightarrow 2 sin 4 theta sin 3 theta`
`=cos (4 theta-3 theta)-cos (4 theta+3 theta)`
`=cos theta-cos 7 theta`
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