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If A+B+C=(3pi)/2, t h e ncos2A+cos2B+cos...

If `A+B+C=(3pi)/2, t h e ncos2A+cos2B+cos2C` is equal to (a) `1-4cos Acos BcosC` (b) `4sinAsinBsinC` (c) `1+2cosAcosBcosC` (d) `1-4sinAsinBsinC`

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