18.
如图,△ABC是⊙O的内接三角形,∠A=25°,则∠OBC的度数为( )
| A. | 50° | B. | 25° | C. | 65° | D. | 75° |
16.
如图,P为线段AB的黄金分割点,且AP>BP,则下列结论成立的个数是( )
(1)$\frac{BP}{AP}=\frac{AP}{AB}$;(2)AB:AP=AP:PB;(3)BP2=AP•AB;(4)$\frac{AP}{AB}$≈0.618.
(1)$\frac{BP}{AP}=\frac{AP}{AB}$;(2)AB:AP=AP:PB;(3)BP2=AP•AB;(4)$\frac{AP}{AB}$≈0.618.
| A. | 1个 | B. | 2个 | C. | 3个 | D. | 4个 |
12.下来各数中,比-1小的数是( )
0 308491 308499 308505 308509 308515 308517 308521 308527 308529 308535 308541 308545 308547 308551 308557 308559 308565 308569 308571 308575 308577 308581 308583 308585 308586 308587 308589 308590 308591 308593 308595 308599 308601 308605 308607 308611 308617 308619 308625 308629 308631 308635 308641 308647 308649 308655 308659 308661 308667 308671 308677 308685 366461
| A. | 0 | B. | 1 | C. | -1 | D. | -$\sqrt{2}$ |