1cos()等于()A.B.C D解析:cos()coscos(6)cos.答案:C2sin600tan240的值是()A B.C D.解析:sin600tan240sin(360240)tan(18060)sin240tan60sin(18060)tan60sin60tan60.答案:B3已知sin(45),则sin(135)_.解析:sin(135)sin180(45)sin(45).答案:4已知(0,),tan(),则sin_.解析:由于tan()tan,则tan,解方程组得sin,又(0,),所以sin0.所以sin.答案:5化简.解:原式tan.