3.学校新开设了航模、彩绘两个社团,如果征征、舟舟两名同学每人随机选择参加其中一个社团,那么征征和舟舟选到同一社团的概率为( )
| A. | $\frac{2}{3}$ | B. | $\frac{1}{2}$ | C. | $\frac{1}{3}$ | D. | $\frac{1}{4}$ |
2.如果关于x的一元二次方程x2-6x+m=0有两个相等的实数根,则m所满足的条件是( )
| A. | m<9 | B. | m>9 | C. | m=9 | D. | m≤9 |
18.
如图,为了对一颗倾斜的古杉树AB进行保护,需测量其长度:在地面上选取一点C,测得∠ACB=45°,AC=24m,∠BAC=66.5°,(参考数据:$\sqrt{2}$≈1.414,sin66.5°≈0.92,cos66.5°≈0.40,tan66.5°≈2.30).则这颗古杉树AB的长约为( )
0 294441 294449 294455 294459 294465 294467 294471 294477 294479 294485 294491 294495 294497 294501 294507 294509 294515 294519 294521 294525 294527 294531 294533 294535 294536 294537 294539 294540 294541 294543 294545 294549 294551 294555 294557 294561 294567 294569 294575 294579 294581 294585 294591 294597 294599 294605 294609 294611 294617 294621 294627 294635 366461
| A. | 7.27 | B. | 16.70 | C. | 17.70 | D. | 18.18 |