题目

 I don’t usually have ________ breakfast at home, but I always eat ________ good supper at home   A) /; /             B) a; a            C)a; /            D) /; a 答案：D已知sinα-sinβ=-13，cosα+cosβ=12，α∈(0，π2)，β∈(0，π2)，则tan(α-β)= ．