Разложите на множители cosb-sinb*sin2b= сosb-sin2b-cos3b= заранее

1) cosb-sinb×sin2b= cosb-sinb×2×sinb×cosb= cosb-2×sin^2b×cosb= cosb(1-2sin^2 b)= cosb×cos2b 2) cosb-sin2b-cos3b= cosb-sin2b-cos(2b+b)= cosb-2sinbcosb-cos2bcosb-sin2bsinb= cosb-sin2b-cos2bcosb-sin2bsinb= cosb-cos2bcosb-sin2b-sin2bsinb= cosb(1-(1+sinb))