1cos70cos335sin110sin25的结果是()A1B.C. D.解析:原式cos70cos(36025)sin(18070)sin25cos70cos25sin70sin25cos(7025)cos45.答案:B2sin14cos16sin76cos74的值是()A. B.C D解析:sin14cos16sin76cos74cos76cos16sin76sin16cos(7616)cos60.答案:B3sin100sin(160)cos200cos(280)_.解析:原式sin(18080)sin(18020)cos(18020)cos(36080)sin80sin20cos20cos80cos(8020)cos60.答案:4已知sin,(,),则cos()的值为_解析:sin,(,),cos,cos()coscossinsin.答案:5已知,(,),sin(),sin(),求cos()的值解:,(,),sin(),sin(),(,2),(,),cos(),cos(),cos()cos()()cos()cos()sin()sin()()().