3.
如图,正方形ABCD内接于圆O:x2+y2=2,M,N分别为边AB,BC的中点,已知点P(2,0),当正方形ABCD绕圆心O旋转时,$\overrightarrow{PM}•\overrightarrow{ON}$的取值范围是( )
| A. | [-1,1] | B. | $[{-\sqrt{2},\sqrt{2}}]$ | C. | [-2,2] | D. | $[{-\frac{{\sqrt{2}}}{2},\frac{{\sqrt{2}}}{2}}]$ |
20.单调递减的数列{an}的通项公式an=$\left\{\begin{array}{l}{(1-3a)n+14a,n≤8}\\{lo{g}_{a}(n-8),n>8}\end{array}\right.$,则正数a的取值范围是( )
| A. | ($\frac{1}{3}$,1) | B. | ($\frac{1}{3}$,$\frac{4}{5}$) | C. | (0,$\frac{4}{5}$) | D. | (0,1) |
19.已知椭圆C:$\frac{{x}^{2}}{{a}^{2}}+\frac{{y}^{2}}{{b}^{2}}=1$(a>b>0)的右焦点为F2,O为坐标原点,M为y轴上一点,点A是直线MF2与椭圆C的一个交点,且|OA|=|OF2|=2|OM|,则椭圆C的离心率为( )
| A. | $\frac{1}{3}$ | B. | $\frac{2}{5}$ | C. | $\frac{\sqrt{5}}{5}$ | D. | $\frac{\sqrt{5}}{3}$ |
18.不等式|x|•(1-2x)>0的解集是( )
| A. | $(-∞,\frac{1}{2})$ | B. | (-∞,0)∪$(0,\frac{1}{2})$ | C. | $(\frac{1}{2},+∞)$ | D. | $(0,\frac{1}{2})$ |
16.设曲线y=xn+1(n∈Z*)在点(1,1)处的切线与x轴的交点的横坐标为xn,则x1•x2•x3…•xn的值为( )
0 238975 238983 238989 238993 238999 239001 239005 239011 239013 239019 239025 239029 239031 239035 239041 239043 239049 239053 239055 239059 239061 239065 239067 239069 239070 239071 239073 239074 239075 239077 239079 239083 239085 239089 239091 239095 239101 239103 239109 239113 239115 239119 239125 239131 239133 239139 239143 239145 239151 239155 239161 239169 266669
| A. | $\frac{1}{n}$ | B. | $\frac{n}{n+1}$ | C. | $\frac{1}{n+1}$ | D. | 1 |