Bcos2的精选

问题详情：等于()(A)sin2－cos2                         (B)cos2－sin2(C)±(sin2－cos2)              (D)sin2＋cos2【回答】A.原式＝＝＝|sin2－cos2|，∵sin2>0，cos2<0，∴原式＝sin2－cos2.知识点：...