factorize sin4a - sin2a
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sin 4 a - sin 2 a
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= sin 2 ( 2a ) - sin 2a
= 2 sin2a cos2a - sin 2a
= sin2a ( 2 cos2a - 1 )
= sin2a ( 2 ( cos^2 a - sin^2 a ) - 1 )
=sin2a {2 ( cosa - sina ) ( cosa + sina ) -1}
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sin 4 a - sin 2 a
_______________________________
= sin 2 ( 2a ) - sin 2a
= 2 sin2a cos2a - sin 2a
= sin2a ( 2 cos2a - 1 )
= sin2a ( 2 ( cos^2 a - sin^2 a ) - 1 )
=sin2a {2 ( cosa - sina ) ( cosa + sina ) -1}
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sma6660:
hw did you introduce that cos there
its formulas , sin2A = 2sinAcosA and cos2A = cos^2A - sin^2A
i used it there
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