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Sin3x=-4sin^(3)x+3sinx |
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Answer» Since the angle sum FORMULA of sine is:sin(α+β)=sinαcosβ+cosαsinβ ,and the double angle formula of cosine:cos(2α)=cos2α−sin2α=2cos2α−1=1−2sin2αthen:sin(3X)=sin(2x+x)=sin(2x)cosx+cos(2x)sinx==(2sinxcosx)⋅cosx+(1−2sin2x)sinx==2sinxcos2x+sinx−2sin3x= =2sinx(1−sin2x)+sinx−2sin3x= =2sinx−2sin3x+sinx−2sin3x= =3sinx−4sin3x .if this ANSWER is helpful to you please MARK me as a BRAIN list |
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