5.满足下列条件的△ABC,不是直角三角形的是( )
| A. | ∠A:∠B:∠C=5:12:13 | B. | a:b:c=3:4:5 | ||
| C. | ∠C=∠A-∠B | D. | b2=a2-c2 |
4.
如图,直角三角形三边向外作正方形,字母A所代表的正方形的面积为( )
| A. | 4 | B. | 8 | C. | 16 | D. | 64 |
3.在平面直角坐标系中,点A坐标为(4,5),点A向左平移5个单位长度到点A1,则点A1的坐标是( )
| A. | (-1,5) | B. | (0,5) | C. | (9,5) | D. | (-1,0) |
2.下列实数中,无理数是( )
| A. | $\frac{1}{3}$ | B. | $\sqrt{16}$ | C. | $\sqrt{7}$ | D. | $\root{3}{-27}$ |
20.若线段AB=1,点C是AB的黄金分割点,且AC>BC,则AC=( )
0 294488 294496 294502 294506 294512 294514 294518 294524 294526 294532 294538 294542 294544 294548 294554 294556 294562 294566 294568 294572 294574 294578 294580 294582 294583 294584 294586 294587 294588 294590 294592 294596 294598 294602 294604 294608 294614 294616 294622 294626 294628 294632 294638 294644 294646 294652 294656 294658 294664 294668 294674 294682 366461
| A. | $\sqrt{5}$-1 | B. | $\sqrt{5}$-2 | C. | $\frac{{\sqrt{5}-1}}{2}$ | D. | $\frac{{\sqrt{5}-2}}{2}$ |