13.已知函数$f(x)=\left\{\begin{array}{l}{2^x},x≤0\\{log_3}x,x>0\end{array}\right.$,则$f[f(\frac{1}{27})]$的值为( )
A. | $\frac{1}{8}$ | B. | 8 | C. | -8 | D. | $-\frac{1}{8}$ |
12.函数$f(x)=\frac{{\sqrt{2-x}}}{x-1}+{log_2}(x+1)$的定义域为( )
A. | (-1,+∞) | B. | [-1,1)∪(1,2] | C. | (-1,2] | D. | (-1,1)∪(1,2] |
8.在直三棱柱ABC-A1B1C1中,AB=AC=BC=2,AA1=1,则点A到平面A1BC的距离为( )
0 252769 252777 252783 252787 252793 252795 252799 252805 252807 252813 252819 252823 252825 252829 252835 252837 252843 252847 252849 252853 252855 252859 252861 252863 252864 252865 252867 252868 252869 252871 252873 252877 252879 252883 252885 252889 252895 252897 252903 252907 252909 252913 252919 252925 252927 252933 252937 252939 252945 252949 252955 252963 266669
A. | $\frac{{\sqrt{3}}}{4}$ | B. | $\frac{{\sqrt{3}}}{2}$ | C. | $\frac{{3\sqrt{3}}}{4}$ | D. | $\sqrt{3}$ |