8.若椭圆经过原点,且焦点分别为F1(1,0),F2(4,0),则其离心率为( )
| A. | $\frac{3}{5}$ | B. | $\frac{2}{3}$ | C. | $\frac{3}{4}$ | D. | $\frac{1}{2}$ |
5.设l是直线,α,β是两个不同的平面,则下列四个命题:
(1)若l∥α,l∥β,则α∥β
(2)若l∥α,l⊥β,则α⊥β
(3)若α⊥β,l⊥α,则l⊥β
(4)若α⊥β,l∥α,则l⊥β
中真命题有( )个.
(1)若l∥α,l∥β,则α∥β
(2)若l∥α,l⊥β,则α⊥β
(3)若α⊥β,l⊥α,则l⊥β
(4)若α⊥β,l∥α,则l⊥β
中真命题有( )个.
| A. | 0 | B. | 1 | C. | 2 | D. | 3 |
4.已知一平摆线的滚动圆的半径为2,且φ=π,求摆线的参数方程( )
0 233356 233364 233370 233374 233380 233382 233386 233392 233394 233400 233406 233410 233412 233416 233422 233424 233430 233434 233436 233440 233442 233446 233448 233450 233451 233452 233454 233455 233456 233458 233460 233464 233466 233470 233472 233476 233482 233484 233490 233494 233496 233500 233506 233512 233514 233520 233524 233526 233532 233536 233542 233550 266669
| A. | $\left\{\begin{array}{l}x=4\\ y=2π\end{array}\right.$ | B. | $\left\{\begin{array}{l}x=2π\\ y=4\end{array}\right.$ | C. | $\left\{\begin{array}{l}x=-2\\ y=2π\end{array}\right.$ | D. | $\left\{\begin{array}{l}x=2π\\ y=-2\end{array}\right.$ |