积化和差：sinαcosβ=[sin(α+β)+sin(α-β)]/2cosαsinβ=[sin(α+β)-sin(α-β)]/2cosαcosβ=[cos(α+β)+cos(α-β)]/2sinαsinβ=[sin(α+β)-sin(α-β)]/2和差化积：sinx+siny=2sin[(x+y)/2]cos[(x-y)/2]s...