6.
如图,在Rt△ABC中,∠C=90°,AC=12,BC=5,CD⊥AB于点D,则cot∠BCD的值为( )
| A. | $\frac{5}{13}$ | B. | $\frac{5}{12}$ | C. | $\frac{12}{5}$ | D. | $\frac{12}{13}$ |
5.
如图,已知点D、E分别在△ABC的边BA、CA的延长上,下列给出的条件中,不能判定DE∥BC的是( )
| A. | BD:AB=CE:AC | B. | DE:BC=AB:AD | C. | AB:AC=AD:AE | D. | AD:DB=AE:EC |
4.如果△ABC∽△DEF,相似比为2:1,且△DEF的面积为4,那么△ABC的面积为( )
0 279380 279388 279394 279398 279404 279406 279410 279416 279418 279424 279430 279434 279436 279440 279446 279448 279454 279458 279460 279464 279466 279470 279472 279474 279475 279476 279478 279479 279480 279482 279484 279488 279490 279494 279496 279500 279506 279508 279514 279518 279520 279524 279530 279536 279538 279544 279548 279550 279556 279560 279566 279574 366461
| A. | 1 | B. | 4 | C. | 8 | D. | 16 |