13.在△ABC中,AB=AC=6,cos∠B=$\frac{2}{3}$,以点B为圆心,AB为半径作圆B,以点C为圆心,半径长为13作圆C,圆B与圆C的位置关系是( )
| A. | 外切 | B. | 相交 | C. | 内切 | D. | 内含 |
12.
如图,在△ABC中,中线AD、CE交于点O,设$\overrightarrow{AB}$=$\overrightarrow{a}$,$\overrightarrow{BC}$=$\overrightarrow{b}$,那么向量$\overrightarrow{AO}$用向量$\overrightarrow{a}$、$\overrightarrow{b}$表示为( )
0 294589 294597 294603 294607 294613 294615 294619 294625 294627 294633 294639 294643 294645 294649 294655 294657 294663 294667 294669 294673 294675 294679 294681 294683 294684 294685 294687 294688 294689 294691 294693 294697 294699 294703 294705 294709 294715 294717 294723 294727 294729 294733 294739 294745 294747 294753 294757 294759 294765 294769 294775 294783 366461
| A. | $\overrightarrow{a}$+$\frac{1}{2}$$\overrightarrow{b}$ | B. | $\frac{2}{3}$$\overrightarrow{a}$+$\frac{1}{3}$$\overrightarrow{b}$ | C. | $\frac{2}{3}$$\overrightarrow{a}$+$\frac{2}{3}$$\overrightarrow{b}$ | D. | $\frac{1}{2}$$\overrightarrow{a}$+$\frac{1}{4}$$\overrightarrow{b}$ |