13.
如图,E点是AD延长线上一点,下列条件中,不能判定直线AB∥CD的是( )
| A. | ∠1=∠2 | B. | ∠3=∠4 | C. | ∠A=∠CDE | D. | ∠C+∠1+∠4=180° |
11.下列运算中,正确的是( )
| A. | (a+2)2=a2+4 | B. | 2x+3y=5xy | C. | x6÷x3=x2 | D. | (-x3)2=x6 |
7.
如图所示,分别以n边形的顶点为圆心,以1cm为半径画园,当n=2017时则图中阴影部分的面积之和为( )
0 295372 295380 295386 295390 295396 295398 295402 295408 295410 295416 295422 295426 295428 295432 295438 295440 295446 295450 295452 295456 295458 295462 295464 295466 295467 295468 295470 295471 295472 295474 295476 295480 295482 295486 295488 295492 295498 295500 295506 295510 295512 295516 295522 295528 295530 295536 295540 295542 295548 295552 295558 295566 366461
| A. | πcm2 | B. | 2πcm2 | C. | 2016πcm2 | D. | 2017πcm2 |