=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