Question

f(sinx)=3-cos2x,则f(cosx)等于(    )

A.3-cos2x          B.3-sin2x                 C.3+cos2x          D.3+sin2x

Answer 1

解析:f(sinx)=3-(1-2sin²x)=2+2sin²x,

f(cosx)=2+2cos²x=2+1+cos2x=3+cos2x.

答案: C