Prove that


=Sin3x+sin2x-sinx


= (sin3x- sinx)+sin2x


= ( 2cossin) + sin2x


= 2cos2xsinx +sin2x


= 2cos2xsinx + 2sinxcosx


= 2sinx (cos2x + cosx )


= 2sinx (2cos cos )


= 4sinxcos cos


Using the formula,


sinA - sinB = 2cos sin


cosA + cosB = 2coscos


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