13.如果p是q的充分不必要条件,r是q的必要不充分条件;那么( )
| A. | ¬p?¬r | B. | ¬p⇒¬r | C. | ¬p?¬r | D. | p?r |
8.设变量x,y满足约束条件$\left\{{\begin{array}{l}{x-y≥0}\\{x+y≥1}\\{x≤2}\end{array}}\right.$,则目标函数z=-2x+y的最大值为( )
| A. | 2 | B. | $\frac{1}{2}$ | C. | -2 | D. | $-\frac{1}{2}$ |
6.若$cos(\frac{π}{2}-α)=\frac{1}{3}$,$\frac{π}{2}<α<π$,则sin2α=( )
| A. | $-\frac{{2\sqrt{2}}}{9}$ | B. | $-\frac{{2\sqrt{2}}}{3}$ | C. | $-\frac{{4\sqrt{2}}}{9}$ | D. | $-\frac{4}{9}$ |
5.若$\overrightarrow a=(1,\sqrt{3})$,$\overrightarrow b=(3,0)$,则$\overrightarrow a,\overrightarrow b$的夹角为( )
0 235522 235530 235536 235540 235546 235548 235552 235558 235560 235566 235572 235576 235578 235582 235588 235590 235596 235600 235602 235606 235608 235612 235614 235616 235617 235618 235620 235621 235622 235624 235626 235630 235632 235636 235638 235642 235648 235650 235656 235660 235662 235666 235672 235678 235680 235686 235690 235692 235698 235702 235708 235716 266669
| A. | $\frac{π}{3}$ | B. | $\frac{2π}{3}$ | C. | $\frac{π}{6}$ | D. | $\frac{5π}{6}$ |