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If A+B+C=(3pi)/2 , then cos2A+cos2B+cos...

If `A+B+C=(3pi)/2` , then `cos2A+cos2B+cos2C` is equal to a.`1-4cos Acos B cos C` b. `4sinAsin B sin C` c.`1+2cos A\cos Bcos C` d. `1-4sinAsin BsinC`

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ALLEN-TRIGONOMETRIC RATIOS AND IDENTITIES-All Questions
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