cos（α+β）*cos（α-β）=(cosαcosβ-sinαsinβ)*(cosαcosβ+sinαsinβ)=cos^2(α)cos^2(β) -sin^2(α)sin^2(β) = cos^2(α)(1-sin^2(β) )-(1- cos^2(α)) sin2β= cos^2(α)- cos^2(α)sin^2(β) - sin^2(...