1sin165等于()Asin15 Bcos15Csin75 Dcos75解析sin165sin(9075)cos75.选D.答案D2已知sin,那么cos()A B C. D.解析sinsinsincos.答案C3如果cos(A),那么sin()A B. C D.解析cos(A)cosA,cosA,sincosA,故选B.答案B4已知sin,则cos的值为()A. B C. D解析coscossin.选C.答案C5已知tan2,求的值解2.