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绝密 ★ 启用前 x π
项A错;对于选项B, f(x)sin ,把函数y f(x)图象上所有点的横坐标伸长到原来
2 12
2025 届高三上学期学情诊断
x π π
的 2 倍,纵坐标不变,得到 y sin ,再把所得曲线向左平移 个单位长度,得到
4 12 3
数学解析
2024.12
1 π π x π π
g(x)sin( (x ) )sin( ),其图象不关于点 , 0中心对称,故选项B 错;对于
4 3 12 4 6 4
一、选择题:本题共8小题,每小题5分,共40分. 在每小题给出的四个选项中,只有一个选项是正确
7π
的.请把正确的选项填涂在答题卡相应的位置上. 选项C,f(x)sin2x ,把函数y f(x)图象上所有点的横坐标伸长到原来的2倍,纵坐
12
5 5(2i) 7π π
1.A【解析】 2i,2i的共轭复数是2i.故选A. 标 不 变 , 得 到 y sinx , 再 把 所 得 曲 线 向 左 平 移 个 单 位 长 度 , 得 到
2i (2i)(2i) 12 3
1 π 7π π π
2.C【解析】由AB B得B A.当a 0时,B ,满足B A;当a 0时B , g(x)sinx sinx ,其图象关于点 , 0中心对称,选项C 正确;对于选项
a 3 12 4 4
1 1 1 π
因为B A,所以 1或 ,解得a 1或a 2.故选C. D, f(x)sin2x ,把函数y f(x)图象上所有点的横坐标伸长到原来的2倍,纵坐标不
a a 2 12
1 x2 3x 1 1 π π
3.B【解析】f (x) x 3 ,因为a ,a 为函数 f (x) x2 ln x 3x 1 变 , 得 到 y sinx , 再 把 所 得 曲 线 向 左 平 移 个 单 位 长 度 , 得 到
x x 2 7 2 12 3
的两个极值点,所以a a 3,因为 a 为等差数列,所以a a 3.故选B. π 5π π
2 7 n 4 5 g(x)sinx sinx ,其图象不关于点 , 0中心对称,选项D错.故选C.
3 12 12 4
4.B【解析】因为 AB AC 2AO ,所以BC 是圆O的直径.又因为 AB AC ,所以ABC是
7.A【解析】因为210 2024211,所以10log 202411,1log 2024332,所以
2 2
以A为直角的等腰直角三角形.所以
BA
在
BC
上的投影向量为
BO
.故选B.
2024 253
f (log 2024)23 f (log 20249)232log 2 20249 .故选A.
5.D【解析】m与 内所有的直线都垂直是m的充要条件,选项A错;根据面面垂直的 2 2 26 8
性质定理,缺少条件m,故也不是m的充分不必要条件,选项B错;由m与 内无 8.C【解析】由 f(x) f(x1)得 f (x1) f (x)c,其中c为常数,令x 0得 f (1) f (0)c,
数条直线垂直不能推出m,所以不是m的充分不必要条件,选项C 错;由l ,l , 又 f(0)0, f(1)2,得c 2, f (x1) f (x)2.所以 f (n)2(n1)22n,nN .
得//,又因为m,所以m,反之,由m推不出l ,l ,m,所以
1210
f (1) f (2) f (22) f (29)(2 1222 29)2 2046.故选C.
l ,l ,m是m的一个充分不必要条件,选项D正确.故选D. 12
x 7π 二、选择题:本题共 3 小题,每小题6分,共18分.在每小题给出的选项中,有多项符合题目要求.全
6.C【解析】对于选项A, f(x)sin ,把函数y f(x)图象上所有点的横坐标伸长到
2 12 部选对得6分,部分选对的得部分分,选对但不全的得部分分,有选错的得0分.
x 7π π
原来的 2 倍,纵坐标不变,得到 y sin ,再把所得曲线向左平移 个单位长度,得
4 12 3 9.AC【解析】由 y x3单调递增,知a3 b3 ,故选项 A 正确;c0时选项 B 不正确;
1 π 7π x π x π a b a b
到g(x)sin((x ) )sin cos ,其图象不关于点 , 0中心对称,故选 2 2,当且仅当a b时等号成立,因为a b0,所以等号不成立,故选项C
4 3 12 4 2 4 4 b a b a
数学试卷答案 第1页(共9页)
{#{QQABZQYAogAoAAIAARhCEwFSCkGQkgCACagOBEAEoAABiRNABAA=}#}正确;对于函数 y xsinx,y1cosx0,所以 y xsinx单调递增,又a b0,得
asina bsinb,故选项D不正确.故选AC.
π π π
10. BCD 【 解 析 】 f ( )sin(sin )cos(cos )sin1cos0sin11 ,
2 2 2
π π
f ( )sin(sin( ))
2 2
π π π
cos(cos( ))sin(1)cos0sin11,得 f ( ) f ( ),所以 f(x)不是偶函数,故选项
2 2 2
A 错误; f (x2π)sin(sin(x2π))cos(cos(x2π))sin(sinx)cos(cosx) f (x),所以 再由OA 底面OBC 可得 ND 底面OBC ,而 MD 平面OBC ,故 ND DM .又因为
OM
f(x)是以2π为周期的周期函数,故选项B正确; ,所以DM //BC 且DM 2 2,所以可得
OB
f (π-x)sin(sin(π-x))cos(cos(π-x))sin(sinx)cos(cos(x)) f (x),所以 f(x)关于直
1 2 6
MN DM2 DN2 22 (1)2 32 21 3( )2 ,所以B 选项错误;
π
线x 对称,故选项C 正确; 3 3 3
2
OD AN 1 1 OM
C选项,因为1,所以 ,即OD ,又因为 ,所以OM OB ,
π π
对于选项 D,由 f(x)关于直线x 对称,只需看当x(0, ]时,1 f(x)0是否成立即可.当 OC AC OB
2 2
再由 DN //OA 可得,点 N 到平面 OAM 的距离等于点 D 到平面 OAM 的距离,故有
π
x(0, ] 时, 0sinx1 , 0cosx1 , 0sin(sinx)sin1 , cos1cos(cosx)1,所以 V V V V ,因为OA底面OBC,所以OA即为三棱锥AODM 的高,
2 OAMN NOAM DOAM AODM
1 1 1 1 1
sin(sinx)cos(cosx)1 , 又 因 为 sinxcosx 2sin(x
π
) 2
π
, 所 以
从而V
OAMN
V
AODM
3
S
ODM
OA
3
2
1
6
,是定值,所以C 选项正确;
4 2
D选项,满足PA PO且PB PC的点P的轨迹是分别以OA, BC 为直径的球相交所得的圆,
π π
0sinx cosx ,
2 2 如图下左所示,其轴截面如下右图所示,
π
所以sin(sinx)sin( cosx) cos(cosx) ,所以1 f(x)0,故选项D正确.故选BCD.
2
3
11.ACD【解析】A 选项,三棱锥O ABC的外接球是边长为1的正方体的外接球,其半径R ,
2
2
3 3
所以表面积为4πR2 4π 4π 3π,所以A选项正确;
2 4
B 选项,在三棱锥O ABC中,由OA,OB,OC 两两垂直可得OA底面OBC.如图所示,在
OD AN
线段OC 上取一点D,使得 ,即得DN //OA且DN 1,
OC AC
数学试卷答案 第2页(共9页)
{#{QQABZQYAogAoAAIAARhCEwFSCkGQkgCACagOBEAEoAABiRNABAA=}#}该圆的直径为线段HG,OA的中点E是OA为直径的球的球心,BC中点F 是BC为直径的球 四、解答题:本题共5小题,共77分. 解答应写出文字说明、证明过程或演算步骤.
15.【解析】考查方向:构造常数列/累加法求通项+分组求和、并项求和、等比数列求和
1 2
的球心,可得EG
1
,FG
2
,EF
3
,从而GI
2 2
6
,点P所形成的轨迹长度为
(1)【法一】构造常数列
2 2 2 3 6
由a2 a2 2n1 =(n+1)2 n2 (nN),a 1,可得a2 (n+1)2 a2 n2 a2 12 0 ,
2 n1 n 1 n1 n 1
6 6 故数列 a2 n2 是恒为0的常数列,所以a2 n2,······································································· 5分
2π π,所以D选项正确.故选ACD. n n
6 3
又因为数列 a 为正项数列,所以a n (nN).······································································· 6分
n n
【法二】累加法
三、填空题:本题共3小题,每小题5分,共15分.
1 π 1 1 1 由题意得:n2且nN,有
12. 【解析】因为sin( ) ,所以cos ,所以cos22cos21 .
2 2 2 2 2
a2 a2 2(n1)1 2n1,
π 1 n n1
13. 【解析】由πrl πr2 π且2πr πl,得r2 , h l2 r2 3r2 1 ,所以 a2 a2 2(n2)1 2n3,
9 3 n1 n2
1 π
V πr2h . a2 a2 2215,
3 2
3 9
a2 a2 2113,
2 1
a2 b2 c2
14.4 3,[2, 6]【解析】由题意可得( ) 即可,当△ABC为等边三角形时有 (n1)(32n1)
S min 将以上各式相加,得a2 a2 35(2n3)(2n1) n2 1 ,
n 1 2
a2 b2 c2 a2 b2 c2
4 3.下证对于任意的三角形都有( ) 4 3. 将a 1代入上式即得a2 n2,且当n1时也成立,所以a2 n2,
S S min 1 n n
证明过程如下: 又因为数列 a 为正项数列,所以a n (nN).·····································································6分
n n
a2 b2 c2 4 3S 2 b2 c2 2bccosA2 3bcsinA (2)由(1)可得b (1)nn3n,令c (1)nn,其前2n项和为T ,
n n 2n
2 b2c2 2bc 3sin AcosA 2 b2c2 4bcsin A 则T 1234(2n1)2nn,··············································································9分
6 2n
2 b2c2 4bc2 bc 20 ,
又因为3132 32n
3(132n)
3(32n 1)
32n13
,························································12分
13 2 2
π
当A 且bc等号成立,即△ABC为等边三角形时等号成立.所以的最大值为4 3.
3
32n13
所以S n .··························································································· 13分
2n 2
当取得最大值时,△ABC为等边三角形,如右图所示,取AB的中点D,
16.【解析】正弦定理+最值
2 2 2
则有PAPB PDDA PDDA PD DA PD 3 ,
bcosC 3bsinC sinBcosC 3sinBsinC
(1)根据正弦定理, 1可化为 1,1分
ac sin AsinC
由图可得1|PD|3,所以 PAPB 的取值范围是[2, 6].
数学试卷答案 第3页(共9页)
{#{QQABZQYAogAoAAIAARhCEwFSCkGQkgCACagOBEAEoAABiRNABAA=}#}又因为BE DG,AB AD,所以tan tan,从而;········································7分
sinBcosC 3sinBsinC sin AsinC
sinBcosC 3sinBsinC sin(BC)sinC (2)以A为坐标原点,分别以AB,AD,AA 的方向为x轴、y轴、z 轴的正方向建立空间直角坐
1
sinBcosC 3sinBsinC sinBcosC sinCcosBsinC 标系.
sinC( 3sinBcosB1)0.
则E(1,0,tan),G(0,1,tan),所以AE (1,0,tan),AG (0,1,tan),····························9分
·············································································································································5分
因为C(0, π),所以sinC 0,故有 3sinBcosB10,进而有sin(B π ) 1 ,因为B(0, π), 设平面AEFG的法向量n (x,y,z),则有
AEn
1
xztan0
,令z 1,则有
6 2 1
AGn yztan0
π π 5π π π π 1
所以B ( , ),故有B ,所以B .································································7分
6 6 6 6 6 3
x tan,y tan,所以n (tan,tan,1),································································· 11分
1
2π π
π
0 A
3
C
2 π π
平面ABCD的法向量n
2
(0,0,1),平面AEFG 与平面ABCD所成角为,则
(2)因为B ,所以 ,进而有 C .·················································8分
3 0C π 6 2 1 1
2 cos|cosn ,n |
1 2 tan2tan21 π
tan2tan2( )1
2
a b 1
由正弦定理可得sin A 3 sinC , 1 1 3
2 1 1 3
tan2 1 2 tan2 1
tan2 tan2
2π 3 1
sin( C) cosC sinC
所以有 a sin A 3 2 2 1 3cosC , 当且仅当tan2 1 ,即 π 时等号成立,························································· 14分
sinC sinC sinC 2 2sinC tan2 4
3
1 3 3 1 3cosC 3 1 3 即平面AEFG与平面ABCD所成角的余弦值的最大值为 .·········································15分
所以S acsinB a ( ) ( ),·······································11分
ABC
2 4 4 2 2sinC 4 2 2tanC
3
18.【解析】(1)显然 y f(x)的图象经过(2,0),当x0时, y 2,所以 f(x)的图象经过
π π 3 3 3 1 3 3
因为
6
C
2
,所以tanC
3
,所以
8
S
ABC
4
(
2
2tanC
)
2
,··························14分 的所有定点的坐标为(2,0)和(0,2)················································································1分
由题知 f(x)ex ax(x2)(ex a)(x1) ex 2a ,····························································2分
3 3
所以ABC面积的取值范围是( , ).·················································································15分
8 2 若以(2,0)为切点, f(2)e2 2a,切线为y (e2 2a)(x2);
17.【解析】直线与平面所成的角,平面与平面所成的角,线面平行的判定定理和性质定理,
若以(0,2)为切点, f(0)2a1,切线为y (2a1)x2;············································ 4分
最值问题
(注:上述两条切线写出一条即可)
(1)由BD//l ,BD平面AEFG,l 平面AEFG可得,BD//平面AEFG,····················2分
(2)①当a0时,ex 2a 0恒成立,
再由BD平面BB D D,平面BB D D平面AEFG EG,所以BD//EG,·······················4分
1 1 1 1
所以当x1时, f(x)0, f(x)在(,1)单调递减,
又因为BE//DG,所以四边形BDGE 为平行四边形,所以BE DG.·······························5分
在正四棱柱ABCD ABC D 中,BB ,DD 均垂直于平面ABCD,所以直线AE、AG与平面 当x1时, f(x)0, f(x)在(1,)单调递增; ··················································5分
1 1 1 1 1 1
ABCD所成的角分别为EAB,GAD,即EAB,GAD,···································· 6分
②当a0时,由 f(x)0,得x 1或x ln 2a . ············································6分
1 2
数学试卷答案 第4页(共9页)
{#{QQABZQYAogAoAAIAARhCEwFSCkGQkgCACagOBEAEoAABiRNABAA=}#}e 1
当ln(2a)1,即a 时, f(x)0恒成立,则 f(x)在R上单调递增,········································ 7分 h(1)e10,所以存在t(0,1),使得h(t)tet 10,即et 即lnt t.当x(0,t)时,
2 t
e
当ln(2a)1时,即a 时,当x1时, f(x)0, f(x)在(,1)单调递增; h(x)0,g(x)0,g(x)单调递减;当x(t,)时,h(x)0,g(x)0,g(x)单调递增.所
2
1
当1 xln(2a)时, f(x)0, f(x)在 1,ln(2a) 单调递减; 以g(x) g(t) lntt1lntt 0
tet
当xln(2a)时, f(x)0, f(x)在 ln(2a), 单调递增; ··················································9分 1
所以 lnxx10也即 f(x2)(lnxx1)e2 0 .··············································17分
xex
e
当ln(2a)1时,即0a 时,
2 1
【证法三】当a 0时, f(x2)(lnxx1)e2 0 x(lnx x1)0.
ex
当xln(2a)时, f(x)0, f(x)在 ,ln(2a) 单调递增;
1 1
令g(x) x(lnxx1) ,g(x) lnx2x,
当ln(2a) x1时, f(x)0, f(x)在(ln(2a),1)单调递减; ex ex
易知g(x)在(0,)上单调递增,x时,g(x);x0时,g(x),所以存在
当x1时, f(x)0, f(x)在 1, 单调递增; ·················································11分
1
t(0,),使得g(t) lnt2t 0,即et lnt2t 即et (t)lntt ,
综上所述:当a0时, f(x)在(,1)单调递减,在(1,)单调递增; et
e 1
当0a 时, f(x)在 ,ln(2a) 单调递增,在(ln(2a),1)单调递减,在 1, 单调递增; 令G(x)ex x ,则G(t)G(lnt),因为G(x)在R 上单调递增,所以lnt t,即et .
2 t
e
当a 时, f(x)在R上单调递增; 当x(0,t)时,g(x)0,g(x)单调递减;当x(t,)时,g(x)0,g(x)单调递增.
2
e 1
当a 时, f(x)在(,1)单调递增,在 1,ln(2a) 单调递减,在 ln(2a), 单调递增.···············12分 所以g(x) g(t) tlntt2t 0 ,所以 f(x2)(lnxx1)e2 0 .·························· 17分
2
et
(3)【证法一】当a 0时, f(x2)(lnxx1)e2 0 ex(xlnxx2x)10.
19.【解析】(1)【法一】由a 2a 1可得a 12 a 1 ,所以数列 a 1 为公比是
n n1 n n1 n
令g(x)ex(xlnxx2x)1,则g(x)ex(xlnxx2xlnx12x1)ex(x1)(lnxx)
2的等比数列,所以a 12n a 1 2n,即得a 2n 1,所以数列的母函数为
1 1 1 n 0 n
令h(x)lnxx,h(x) 1,则h(x)在(0,)上单调递增.又因为h(1)10,h( )1 0,
x e e
f x 2n 1 xn .
1 1
所以存在t( ,1),使得h(t)lntt 0,即lnt t即et .当x(0,t)时,h(x)0,g(x)0, n0
e t
·························································································································· 4分
g(x)单调递减;当x(t,)时,h(x)0,g(x)0,g(x)单调递增.所以
g(x) g(t)et(tlntt2t)10 . 【法二】在 1 Ck1 xn 1Ck1xCk1x2 Ck1 xn 中
1x k nk-1 k k1 nk-1
n0
所以ex(xlnxx2 x)10也即 f(x2)(lnxx1)e2 0 .·········································17分
1
1
令k 1得 C0xn xn 1xx2 xn ,所以
【证法二】当a 0时, f(x2)(lnxx1)e2 0 lnx x10. 1x n
xex
n0 n0
1
1 (x1) 1 (x1)(xex1) 12x22x2 2nxn ,
令g(x) lnxx1,g(x) 1 , 12x
xex x2ex x x2ex
令h(x) xex 1,h(x)(x1)ex 0 ,则h(x)在(0,)上单调递增.又因为h(0)10, f x a
0
a
1
xa
2
x2a
n
xn①
数学试卷答案 第5页(共9页)
{#{QQABZQYAogAoAAIAARhCEwFSCkGQkgCACagOBEAEoAABiRNABAA=}#}2xf x 2a x2a x22a x32a xn1② f x 2 2 4 4 4
0 1 2 n G x
1x 1x 12x 3 1x 12x (12x)2 (12x)3
①②得
12x f x a a 2a x a 2a x2 a 2a x3 a 2a x n
0 1 0 2 1 3 2 n n1 2C0xn 4C02nxn 4C1 2nxn 4C2 2nxn
n n n1 n2
1 n0 n0 n0 n0
0xx2x3xn 1 ,
1x
242n4C1 2n4C2 2n xn [2n1 n2n2 2]xn ,
1 1 1 2 1 1 1 n1 n2
f x n0 n0
12x 1x 12x 12x 12x 1x 12x 1x
所以S 2n1 n2 n2 2.·················································································· 17分
n
(20 21x22x2 2nxn ) (1xx2 xn )
(20 1)(211)x(22 1)x2 (2n 1)xn
2n 1
xn .································································································4分
n0
(2)由题意得G x S S xS x2S xn ①
0 1 2 n
那么xG x S xS x2S x3S xn1 ②
0 1 2 n
①②得
1x G x S S S x S S x2 S S x3 S S x n
0 1 0 2 1 3 2 n n1
a a xa x2a xn g x ,
0 1 2 n
g x
所以G x .·······························································································10分
1x
1
(3)由公式 Ck1 xn 1Ck1xCk1x2 Ck1 xn 可得
1x k nk-1 k k1 nk-1
n0
1
令k 3得 C2 xn
1 x 3 n2
n0
2
所以 2C2 (2x)n (n2)(n1)2nxn a xn
12x 3 n2 n
n0 n0 n0
2
数列{a }的母函数为 f
x
,
n 12x 3
由(2)结论知数列{S }的母函数为
n
数学试卷答案 第6页(共9页)
{#{QQABZQYAogAoAAIAARhCEwFSCkGQkgCACagOBEAEoAABiRNABAA=}#}