题干

德国著名数学家狄利克雷在数学领域成就显著,以其名命名的函数f(x)= {1,x0,x ,称为狄利克雷函数,则关于函数f(x)有以下四个命题:

①f(f(x))=1;

②函数f(x)是偶函数;

③任意一个非零有理数T,f(x+T)=f(x)对任意x∈R恒成立;

④存在三个点A(x1,f(x1)),B(x2,f(x2)),C(x3,f(x3)),使得△ABC为等边三角形.

其中真命题的个数是(   )

A:4

B:3

C:2

D:1

上一题 下一题 0.0难度 选择题 更新时间:2019-12-28 11:09:15

答案(点此获取答案解析)

A

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