若f(cosx)=2-sin2x,则f(sinx)=?A.2-cos2x B.2+sin2x C.2-sin2x D.2+cos2x
问题描述：
若f(cosx)=2-sin2x,则f(sinx)=?A.2-cos2x B.2+sin2x C.2-sin2x D.2+cos2x
答
f(sinx)=f(cos(Pai/2-x))=2-sin2(Pai/2-x)=2-sin(Pai-2x)=2-sin2x
选择C
答
原式=f[cos(π/2-x)]
=2-sin[2(π/2-x)]
=2-sin(π-2x)
=2-sin2x
选C