f(sinx)=3-cos 2x,则f(cos x)=?A.3-cos 2x B.3-sin2x C.3+cos2x D.3+sin2x

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/15 02:13:40

f(sinx)=3-cos 2x,则f(cos x)=?A.3-cos 2x B.3-sin2x C.3+cos2x D.3+sin2x
f(sinx)=3-cos 2x,则f(cos x)=?
A.3-cos 2x B.3-sin2x C.3+cos2x D.3+sin2x

f(sinx)=3-cos 2x,则f(cos x)=?A.3-cos 2x B.3-sin2x C.3+cos2x D.3+sin2x
因为cos2x=1-2sin^2 x
f(sinx)=3-cos 2x=3-1+2sin^2 x=2+2sin^2x
所以
f(cosx)=2+2cos^2 x=2+cos2x+1=3+cos2x
选C

f(sinx)=3-1+2(sinx)^2=2+2(sinx)^2
f(x)=2+2x^2
f(cosx)=2+2(cosx)^2 =3+cos2x
选C