高三数学参考答案
题号 1 2 3 4 5 6 7 8 9 10 11
选项 D A B C A B D A AB BCD ACD
12. 2
13. 0
14. [e2,0]
1.【答案】D
【解析】A[1,4],B[1,),则AB[1,).
2.【答案】A
1 1i 1 i
【解析】 ,故其对应的点位于第一象限.
1i (1i)(1i) 2 2
3.【答案】B
【解析】(2x1)5的展开式的通项为
T Cr2x5r1r Cr1r 25rx5r r0,1,2,3,4,5,
r1 5 5
令Cr1r 25r 40,得r3,所以该项含x的次数为5r2.
5
4.【答案】C
【解析】以抛物线的顶点为原点,对称轴为x轴建立平面直角坐标系,
设抛物线方程为y2 2px(p0)
接收天线的口径为12m,深度为3m,则抛物线上有一点的坐标
为(3,6),代入抛物线方程中,解得 p6 y2 12x, .
p
所以信号处理中心与抛物线顶点的距离为 3m
2
5.【答案】A
【解析】由S S 可得a 0,则2a a 03a ,故a 3a 2a a 14d a ,
4 9 7 3 m 7 m 7 3 1 15
故m15
6.【答案】B
数学试卷参考答案 第1页,共10页 1
【解析】由2a3b 4c0 可得2a3b 4c ,两边平方可得ab ,
4
故 a b (a b )2 a 2 b 2 2a b 10
2
7.【答案】D
【解析】观察函数可知, f(x)为定义在R上的偶函数,在(0,)上递增,
a f log 2 f(log 2) f(log 2) ,由30.011,0log 2 2 1 故bca
1 3 3 3 3
3
8.【答案】A
【解析】设正方体棱长为1,以D为原点,以DA,DC,DD 所在直线分别为x,y,z轴,
1
建立空间直角坐标系,可得D(0,0,0),A(1,0,0),B(1,1,0),C(0,1,0),D (0,0,1) ,
1
因为点E为CD中点,可得E(0, 1 ,0),又设 D F F D ,F(0,0,z),可得
2 1
DF (0,0,z),FD (0,0,1z)
1
所以(0,0,z)(0,0,1z),可得z(1z),
解得z ,所以F(0,0, ),
1 1
由三棱锥D ADE的外接球即为DA,DE,DD 为棱的长
1 1
1
方体的外接球,由DA1,DE ,DD 1,
2 1
1 3 3
得长方体的对角线长为l 12( )212 ,所以D ADE的外接球的半径为R ,
2 2 1 4
1 1 1
即球心O为长方体的对角线的中点,所以O( , , ),
2 4 2
1
设平面BEF的法向量为n(x,y,z),BE (1, ,0),BF (1,1, ),
2 1
1
nBEx y0
由 2 ,令x1,则 y 2,z 1 ,
n B F xy z0
1
1
所以n(1,2, ),
数学试卷参考答案 第2页,共10页 1 3 1
因为O, 所以向量BO( , , )与平面BEF的法向量为n垂直,
2 4 2
1 3 1 1 DF 1
则BOn0,即 1( )(2) ( )0,解得1,所以
2 4 2 DD 2
1
9.【答案】AB
【解析】对于A,若众数为5,则x5,A正确;
对于B,原平均数为6,若平均数不变,则x 6 ,B正确;
对于C,原中位数为6,若中位数不变,则x 6 ,C错误;
对于D,若极差为9,则x 0或12,D错误.
10.【答案】 BCD
【解析】对于A,(2)2(2)2 84,点A在圆O外,A错误;
对于B, k 6(2) 4 ,则直线BC的方程为 y6 4 (x2),
BC (2)4 3 3
即4x3y100 , B正确.
对于C,圆心O到 ABC的三边的距离均为半径2 ,则与三边均相切,C正确;
对于D,设P(2cos,2sin)([0,2π))
,
|PA|2 |PB|2 |PC|2(2cos2)2(2sin2)2(2cos2)2
(2sin6)2(2cos4)2(2sin2)2808sin
3π
88(当 ,即P(0,2)取等)
2
故|PA|2 |PB|2 |PC|2的最大值为88,D正确.
11.【答案】ACD
【解析】对于A,小于等于9的正整数中与9不互质的数为3的倍数,即3,6,9,即
(9)936,A正确;
对于B,取n5,(5)4,(52)(25)20,则(52)2(5),B错误;
对于C,若 p为质数p2,则小于等于 pn的正整数中与 pn不互质的数只有
pn
p的倍数,所以互质的数的数目为 pn pn pn1,
p
数学试卷参考答案 第3页,共10页故 3n 23n1 ,则 S
2(13n)
3n1 ,C正确;
n 13
对于D,由(xy)(x)(y),可知x,y互质,则满足条件的(x,y)有
11 11
12,13,14,15,16,23,25,34,35,45,56共11种,故P(A) ,D正确.
C2 15
6
12.【答案】 2
c
【解析】依题意 a2 b2 ,,可得c2 2,故e 2
a
13.【答案】 0
4 3 3 4
【解析】依题意sin ,cos ,sin ,cos ,
5 5 5 5
3 4 4 3
则cos()coscossinsin ( )0
5 5 5 5
14.【答案】[e2,0]
【解析】由题意得gxaxexe与yxb的图象最多有一个交点,
故关于x的方程axexe xb最多有一个根,
所以H(x)axex ex与yb的图像最多有一个交点,
所以H(x)a(x1)ex1恒大于等于0或恒小于等于0,
当x1时,H(x)10,所以H(x)0恒成立,
令 ,则n(x)a(x2)ex,令n(x)0,解得x2,
n(x) H(x) a(x1)ex 1
当a0时,n(x)1满足题意;
当a0时,n(x)在(,2)上单调递减,在(2,)上单调递增,
当 x 1 1 ,且x 0时 a(x 1)1,则n(x )a(x1)ex0 10 ,
0 a 0 0 0
而n(2)ae2
10,故H(x)a(x1)ex1恒大于等于0或恒小于等于0不成立,
不满足题意;
当a0时,n(x)在(,2)上单调递增,在(2,)上单调递减,
所以n(x) n(2)ae210,解得ae2,综上,a 的取值范围为[e2,0].
max
数学试卷参考答案 第4页,共10页15.解(1)如图,取AB中点O,连接PO,CO.··········································1分
因为PA PB 2,AB 2,所以PA2 PB2 AB2,
即PO AB, ………………………………………………………………………………2分
且PO 1,BO 1.
又因为四边形ABCD是菱形,ABC 60,
所以CO AB,CO 3.
因为PC 2,所以PC2 PO2 CO2,
即PO CO,····························································································4分
因为AB平面ABCD,CO平面ABCD,ABCO O,
所以PO 平面ABCD,
又PO平面PAB,所以平面PAB 平面ABCD.··········································6分
(2)以O为原点,OC ,OB,OP分别为x轴, y轴,z 轴建立空间直角坐标系,则
P(0,0,1),A(0,1,0),
B(0,1,0),D( 3,2,0).
所以PA(0,1,1),
PB (0,1,1),
PC ( 3,0,1),PD ( 3,2,1).··························································7分
设平面PAD的法向量为m(x ,y ,z ),
1 1 1
由 m P A 0 得 y 1 z 1 0 ,不妨取m (1, 3, 3).······························8分
mAD 0 3x y 0
1 1
设平面PBC 的法向量为n (x ,y ,z ),
2 2 2
数学试卷参考答案 第5页,共10页
由 n P B 0 得 y 2 z 2 0 ,不妨取n (1, 3, 3).································10分
nPC 0 3x z 0
2 2
mn 133 1
所以 cosm,n
.························································12分
m n 7 7 7
1
故平面PAD与平面PBC 夹角的余弦值为 .·················································13分
7
1 2 3 cosA 2cosB 3cosC
16.解(1)由 可得 .·················1分
tan A tanB tanC sin A sinB sinC
cosA 2cosB 3cosC
由正弦定理可得 .···············································2分
a b c
故bccosA2accosB 3abcosC.························································4分
1 3
由余弦定理可得 (b2 c2 a2)(a2 c2 b2) (a2 b2 c2) .···············6分
2 2
化简得a2 2b2 3c2.···········································································7分
(2)由题意可知,C为锐角,
1 2 1
a2 b2 (a2 2b2) a2 b2
a2 b2 c2 3 3 3 2
则cosC …………10分
2ab 2ab 2ab 3
2 1
当且仅当 a2 b2即b 2a时取等号.············································11分
3 3
7
此时C最大,且sinC .·····························································12分
3
1 2 7
所以S absinC a2 14 .·······································13分
△ABC
2 2 3
解得a 6.···················································································15分
17.解(1) f(x)ex 22k.···································································1分
当k 1时, f(x)0恒成立,故函数 f(x)在在R单调递增;······················ 2分
数学试卷参考答案 第6页,共10页当k 1时,令 f(x)ex 22k 0得xln(2k2).······························3分
故当x(,ln(2k2))时, f(x)0,函数 f(x)单调递减,
当x(ln(2k2),)时, f(x)0,函数 f(x)单调递增,························5分
综上,当k 1时, f(x)0恒成立,函数 f(x)在R单调递增;
当k 1时,函数 f(x)在(,ln(2k2))上单调递减,
在(ln(2k2),)上单调递增.·······························································6分
(2)令F(x)ex 2x2kxsinx1,x0,F(0)0,······························7分
F(x)ex 22kcosx,x0,F(0)22k.·································8分
令(x) F(x)ex 22kcosx,x0,
而(x)ex sinx0在[0,)恒成立,即F(x)在[0,)单调递增,······10分
故当F(0)22k 0,即k 1时,F(x)F(0)0,F(x)在[0,)单调递增,
F(x) F(0)0在[0,)恒成立;························································12分
当F(0)22k 0,即k 1时,当x时,F(x),
所以,存在x 0,使得x(0,x )时,F(x)0,F(x)单调递减,x(x ,)时,
0 0 0
F(x)0,F(x)单调递增,·································································13分
故由F(0)0可知,x(0,x )时,F(x)0与F(x)0在[0,)恒成立矛盾;
0
·········································································································14分
综上,实数k的取值范围是(,1].························································15分
18.解(1)设事件M “小明在前3次射击中得到2分”,
事件N “这2分均在场景B下获得”.····························································1分
数学试卷参考答案 第7页,共10页4 4 1 4 1 1 1 1 1 129 1 1 1 1
则P(M) ,P(MN) .····3分
5 5 5 5 5 2 5 2 2 500 5 2 2 20
1
P(MN) 20 25
所以P(N |M) .························································ 5分
P(M) 129 129
500
(2)设第n次在场景A下射击为事件M ,
n
4 1
则P P(M )1,P(M |M ) ,P(M |M ) ,······························6分
1 1 n1 n 5 n1 n 2
由全概率公式可得P(M ) P(M )P(M |M )P(M )P(M |M ),···········7分
n1 n n1 n n n1 n
4 1 3 1
即P P (1P ) P ,··························································· 8分
n1 5 n 2 n 10 n 2
5 3 5
则P P ,············································································9分
n1 7 10 n 7
5 2 5 2 3
且P 0,可知数列P 是以首项为 ,公比为 的等比数列,······10分
1 7 7 n 7 7 10
n1 n1
5 2 3 5 2 3
则P ,所以P ;············································11分
n 7 710 n 7 710
k1
4 1 5 3 3
(3)设第k 轮得分期望为E ,则E P (1P ) ,········14分
k k k 5 k 2 7 3510
n
3 3
1
所以前n轮期望总得分为S
n
E
5n
35 10
5n
6
1
3
n
.···17分
n k1 k 7 1 3 7 49 10
10
x2 y2
19.(1)设椭圆 1的半焦距为c,
a2 b2
2a 4
a 2
c 1
由已知可得 ,且b0,解方程得b 3,··································2分
a 2
c1
a2 b2 c2
数学试卷参考答案 第8页,共10页x2 y2
所以椭圆E的标准方程为 1;···························································3分
4 3
(2)由已知直线l的斜率不为0,故设直线l的方程为xmy1,
x2 y2
1
联立 4 3 ,消x可得(3m2 4)y2 6my90,
x my1
方程(3m2 4)y2 6my90的判别式36m2 36(3m2 4)144(m2 1)0,
设A(x ,y ),B(x ,y ),其中 y 0, y 0,
1 1 2 2 1 2
6m 9
由已知 y y , y y ,·················································4分
1 2 3m2 4 1 2 3m2 4
8 4 3m
故x x my 1my 1 ,则R ,
.··················5分
1 2 1 2 3m2 4 3m2 4 3m2 4
x 1
所以直线OR:3mx4y 0,其中m 1 .·················································6分
y
1
点A到直线OR的距离
3mx 4y 3x (x 1)4y2 3x 12
d 1 1 1 1 1 1 .·····························7分
9m2 16 9(x 1)2 16y2 3x2 18x 57
1 1 1 1
令u x 4(6,2),···············································································8分
1
3u 3 3
所以d .··················9分
3u2 42u63
u
63
2
4
u
2 3
63
1
1
2
4
u 3
3
当u 3(x 1)时d 取最小值 .······························································· 10分
1 2
(3)设AF F B,则(1x ,y )(x 1,y ),
2 2 1 1 2 2
y
所以y y ,即 1 ,
1 2 y
2
数学试卷参考答案 第9页,共10页所以
1 y y y2y2 (y y )2 4m2 16 10
1 2 1 2 1 2 2 2 ,···11分
y y y y y y 3m24 3(3m24) 3
2 1 1 2 1 2
16 4
因为m2 0,所以3m2 44,0 ,
3(3m2 4) 3
1 10 10
所以2 ,所以22 1 ,
3 3
1
所以 3.························································································ 12分
3
x y
因为点P为线段OA的中点,所以P 1, 1
,
2 2
x y
因为点G为△BFF 的重心,所以G 2 , 2 ,
1 2 3 3
所以
S S S S S
1 △BFP △FOB △FOP △BOP
1 1 1
1
S S S
△F 1 OB △F 1 OP 2 △AOB
1 1 1 1 1 1 3
1(y ) 1 y 1(y y ) y y ,
2 2 2 2 1 2 2 1 2 2 1 4 2
2
因为点G为△BFF 的重心,所以 BG BO ,
1 2 3
2 2 1 1
所以S S S 1(y y ) (y y ),·························14分
2 △ABG 3 △AOB 3 2 1 2 3 1 2
1 y 3 y 6 y 1 9
所以 S 1 2 1 4 2 y 2 69 6(1)3 3 3 1 , 1 ,3 . 15分
S 1 1 y 44 4(1) 2 4 1 3
2 y y 4 1 4
3 1 3 2 y
2
3 3 1 1 27 S 33
因为函数 f() 在 ,3 上单调递减,所以 1 ,
2 4 1 3 16 S 16
2
S 27 33
即 1 的取值范围为 , .····································································17分
S 16 16
2
数学试卷参考答案 第10页,共10页