cos72(cos72－cos12)＋sin72(sin72－sin12）答案是0._数学解答

cos72(cos72－cos12)＋sin72(sin72－sin12）答案是0.

人气：230 ℃　时间：2020-06-02 20:04:27

解答

cos72(cos72－cos12)＋sin72(sin72－sin12） =[(cos72)^2+(sin72)^2]-(cos72cos12+sin72sin12) =1-cos60 =1/2