已知sina-sinB=-1/3,则（sina-sinB）^2=(sina)^2-2sina*sinB+(sinB)^2 =1/9 (1)已知cosa-cosB=1/2则（cosa-cosB）^2=(cosa)^2-2cosa*cosB+(cosB)^2 =1/4 (2)(1)+(2)= (sina)^2-2sina*sinB+(sinB)^2+(cosa)^2-2cosa*c...