按要求答题。

                                                                                                                            渭川田家

                                                                                                                        （唐）王维

                                                                                          斜光照墟落，穷巷牛羊归。野老念牧童，倚杖候荆扉①。

      【注释】①荆扉：柴门。

求证:AC与☉D相切.

设函数$f\left(x\right)=\left\{\begin{array}{c}{2}^{1-x},x\le 1\\ 1-{\log }_{2}x,x>1\end{array}\right.$，则满足$f\left(x\right)\le 2$的x的取值范围是（   ）