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Prove that: cos^2 2x-cos^2 6x=s in4x s i...

Prove that: `cos^2 2x-cos^2 6x=s in4x s in8x`

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`LHS=cos^2 2x−cos^2 6x`
=`(cos2x−cos6x)(cos2x+cos6x)`
=`−2sin((2x+6x)/2)​.sin((2x−6x​)/2).(−2cos((2x+6x)/2​)cos((2x−6x​)/2))`
=`(2sin4xcos4x)(2sin2xcos2x)`
=`sin4xsin8x`
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