y2x2a2?b231212??1,e??1?m?,m?,a??4,a?2 当0?m?1时,211a44mmx2y2???1 设双曲线的方程为x2?4y2??,(??0),焦距2c?10,c2?25 2.
205 当??0时,
x2??y2?4?1,???4?25,??20;
x2???1,???(?)?25,???20 当??0时,
???4?4)3.(??,?4?4.x??y2(1,?? (4?k)(1?k?)0k,?(k4)?(?1)k?或0,k1,? ?3p3p?3x,???? 2p?6,222y2x25??1,c2??1?4,k?1 5.1 焦点在y轴上,则51kk三、解答题
?y?kx?222221.解:由?2,得,即2x?3(kx?2)?6(2?3k)x?12kx?6?0 2?2x?3y?6 ??144k22?24(?2k23?)k72? 48k 当??722?48?,即0k?66,或k??时,直线和曲线有两个公共点; 3366,或k??时,直线和曲线有一个公共点; 33k 当??722?48?,即0k?k 当??722?48?,即0?66?k?时,直线和曲线没有公共点。 332.解:设点P(t,4t),距离为d,d? 当t?
24t?4t2?5174t2?4t?5 ?1711时,d取得最小值,此时P(,1)为所求的点。 22 26
y2x2?1; 3.解:由共同的焦点F1(0,?5),F2(0,5),可设椭圆方程为2?2aa?25169y2x22??1,a?40 ?1双曲线方程为2?,点在椭圆上,P(3,4)222aa?25b25?b双曲线的过点P(3,4)的渐近线为y?b25?b2x,即4?b25?b2?3,b2?16
y2x2y2x2??1;双曲线方程为??1 所以椭圆方程为
40151694.解:设点P(2cos?,bsin?),x2?2y?4cos2??2bsin???4sin2??2bsin??4
22令T?x?2y,sin??t,(?1?t?1),T??4t?2bt?4,(b?0),对称轴t?b 4当
bb?1,即b?4时,Tmax?T|t?1?2b;当0??1,即0?b?4时, 44Tmax?b2?b?4b??4,0 )ax??4?T|b??4 ?(x2?2ymt?44?2b,b?4?2(数学选修1-1) 第二章 圆锥曲线 [综合训练B组]
一、选择题
y2x22??1,?2?0?k?1 1.D 焦点在y轴上,则22kkx2y2?1; )a?4,c?8,b?43,?2.C 当顶点为(?4,0时,
1648y2x2?1 ,3)a?3,c?6,b?33,? 当顶点为(0?时,
9273.C ΔPF1F2是等腰直角三角形,PF2?F1F2?2c,PF1?22c
PF1?PF2?2a,22c?2c?2a,e?c1??2?1 a2?14.C F1F2?22,AF1?AF2?6,AF2?6?AF1
AF2?AF1?F1F2?2AF1?F1F2cos45?AF1?4AF1?8
22202 27
7(6?AF1)2?AF12?4AF1?8,AF1?,
21727S???22??
22225.D 圆心为(1,?3),设x?2py,p??,x?? 设y?2px,p?221621y; 392,y?9x 2p6.C 垂直于对称轴的通径时最短,即当x?,y??p,ABmin?2p
2二、填空题
5c2k?8?912?,k?4; 1.4,或? 当k?8?9时,e?2?4ak?84c29?k?815?,k?? 当k?8?9时,e?2?a9442y2x281??1,??(?)?9,k??1 2.?1 焦点在y轴上,则81kk??kk?y2?4x23.(4,2) ?,x?8x?4?0,x1?x2?8,y1?y2?x1?x2?4?4
?y?x?2 中点坐标为(x1?x2y1?y2,)?(4,2) 22t2t2222224.???,2? 设Q(,t),由PQ?a得(?a)?t?a,t(t?16?8a)?0,
4422?0a,? t?16?8a?0,t?8a?16恒成立,则8a?16 25. (? 7,0)渐近线方程为y??mx,得m?3,c?27,且焦点在x轴上
x1?x2y1?y2b2y2?y1M(,)6. ?2 设A(x,则中点,得k?, ,y),B(x,y)AB112222ax2?x1kOMy2?y1y22?y122222,kAB?kOM?2,b2x12?ay?1?ab, 2x2?x1x2?x1222222212221y22?y12b2??2 bx2?ay2?ab,得b(x2?x)?a(y2?y)?0,即22x2?x1a22 28
三、解答题
1x2y2??1的a?4,c?2,e?,记点M到右准线的距离为MN 1.解:显然椭圆
21612则
1?e?,MN?2MF,即AM?2MF?AM?MN MN2MF当A,M,N同时在垂直于右准线的一条直线上时,AM?2MF取得最小值,
x2y2??1得Mx??23 此时My?Ay?3,代入到1612而点M在第一象限,?M(23,3)
y2x2??1为焦点在y轴的双曲线; 2.解:当k?0时,曲线
4?8k当k?0时,曲线2y2?8?0为两条平行的垂直于y轴的直线;
x2y2??1为焦点在x轴的椭圆; 当0?k?2时,曲线84k22当k?2时,曲线x?y?4为一个圆;
y2x2??1为焦点在y轴的椭圆。 当k?2时,曲线
84ky2x2y2x2??1的焦点为(0,?3),c?3,设双曲线方程为2??1 3.解:椭圆23627a9?a过点(15,4),则
1615??1,得a2?4,或36,而a2?9, 22a9?ay2x2?a?4,双曲线方程为??1。
452?y2?2px,消去y得 4.解:设抛物线的方程为y?2px,则?y?2x?1?24x2?(2p?4)x?1?0,x1?x2?p?21,x1x2? 24 29
AB?1?k2x1?x2?5(x1?x2)2?4x1x2?5(则p?221)?4??15, 24p2?p?3,p2?4p?12?0,p??2,或6 4?y2??4x,或y2?12x
(数学选修1-1) 第二章 圆锥曲线 [提高训练C组]
一、选择题
1.B 点P到准线的距离即点P到焦点的距离,得PO?PF,过点P所作的高也是中线
?Px?1212,代入到y2?x得Py??,?P(,?) 84842.D PF14,(P1F?1?PF2?P22F)?196,2P?1FP1F?P?2 42F2P?2F(22c?),相减得100
? 2PF1?PF2?96,S123.D MF可以看做是点M到准线的距离,当点M运动到和点A一样高时,MF?MA取
得最小值,即My?2,代入y2?2x得Mx?2 4.A c?4?1,c?2x2y2?1过点Q(2,1 ),3且焦点在x轴上,可设双曲线方程为2?a3?a241x222?1?a?2,?y?1 得2?2a3?a2?x2?y2?625.D ?,x?(kx?2)2?6,(1?k2)x2?4kx?10?0有两个不同的正根
?y?kx?2?2???40?24k?0?154k2? 则?x1?x2?得??k??1 ?0,231?k??10?xx??0122?1?k?6.A kAB?x?x1y2?y1y2?y11,) ??1,而y2?y1?2(x22?x12),得x2?x1??,且(222x2?x12y2?y1x2?x1??m,y2?y1?x2?x?12m 22 在直线y?x?m上,即
30