16.已知数列{an}满足a1=0,an+1=an+2n,那么a2005的值是( )
A. | 2003×2004 | B. | 2004×2005 | C. | 20052 | D. | 2005×2006 |
15.已知数列{an}满足a1=1,an=logn(n+1)(n≥2,n∈N*).定义:使乘积a1•a2•a3…an为正整数的k(k∈N+)叫做“幸运数”,则在[1,2015]内所有“幸运数”的和为( )
A. | 2035 | B. | 2036 | C. | 4084 | D. | 4085 |
13.如图,在△ABC中,已知点D在BC边上,cos∠ADC=$\frac{\sqrt{2}}{3}$,cos∠BAD=$\frac{\sqrt{3}}{3}$,AD=2,则BA的长为( )
A. | $\frac{14\sqrt{3}+4\sqrt{21}}{3}$ | B. | 7$\sqrt{3}$+4 | C. | $\sqrt{3}$+4$\sqrt{7}$ | D. | 7+4$\sqrt{7}$ |
11.$\sqrt{3}$tan10°+4sin10°的值为( )
0 246462 246470 246476 246480 246486 246488 246492 246498 246500 246506 246512 246516 246518 246522 246528 246530 246536 246540 246542 246546 246548 246552 246554 246556 246557 246558 246560 246561 246562 246564 246566 246570 246572 246576 246578 246582 246588 246590 246596 246600 246602 246606 246612 246618 246620 246626 246630 246632 246638 246642 246648 246656 266669
A. | 1 | B. | 2 | C. | 4 | D. | $\frac{1}{2}$ |