保密★启用前泉州市2020届高中毕业班单科质量检查理科数学2020．1注意事项：1．答题前，考生先将自己的姓名、准考证号填写在答题卡上．2．考生作答时，将答案答在答题卡上．请按照题号在各题的答题区域（黑色线框）内作答，超出答题区域书写的答案无效．在草稿纸、试题卷上答题无效．3．选择题答案使用2B 铅笔填涂，如需改动，用橡皮擦干净后，再选涂其它答案标号；非选择题答案使用5.0毫米的黑色中性（签字）笔或碳素笔书写，字体工整、笔迹清楚．4．保持答题卡卡面清洁，不折叠、不破损．考试结束后，将本试卷和答题卡一并交回．三、解答题：共70分．解答应写出文字说明、证明过程或演算步骤．第17~21题为必考题，每个试题考生都必须作答．第22、23题为选考题，考生根据要求作答．（一）必考题：共60分．17．（12分）如图，四棱锥ABCD P -的底面是正方形，⊥PA 平面ABCD ，AE PD ⊥．（1）证明：AE ⊥平面PCD ；（2）若AP AB =，求二面角D PC B --的余弦值．【命题意图】本小题考查线面垂直的判定与性质、二面角的求解及空间向量的坐标运算等基础知识，考查空间想象能力、逻辑推理及运算求解能力，考查化归与转化思想、函数与方程思想等，体现基础性、综合性与应用性，导向对发展数学抽象、逻辑推理、直观想象等核心素养的关注．【试题解析】解法一：（1）因为PA ⊥平面ABCD ，CD ⊂平面ABCD ，所以PA CD ⊥．·········································································································1分又底面ABCD 是正方形，所以AD CD ⊥．·····································································2分又PA AD A = ，所以CD ⊥平面PAD ．······································································3分又AE ⊂平面PAD ，所以CD AE ⊥．···········································································4分又因为AE PD ⊥，CD PD D = ，,CD PD ⊂平面PCD ，·············································5分所以AE ⊥平面PCD ．·······························································································6分（2）因为PA ⊥平面ABCD ，底面ABCD 为正方形，所以PA AB ⊥，PA AD ⊥，AB AD ⊥，分别以AB 、AD 、AP 所在的直线为x 轴、y 轴、z 轴建立空间直角坐标系A xyz -（如图所示）．······································································7分设1PA AB ==，则A 0,0,0（），B 1,0,0（），C 1,1,0（），D 0,1,0（），(0,0,1)P ，11(0,,)22E ，1,0,1PB =- （），1,1,1PC =- （），11(0,,22AE = ．··························································8分由（1）得11(0,,)22AE = 为平面PCD 的一个法向量．·······················································9分设平面PBC 的一个法向量为111()m x ,y ,z = ．由0,0,PB m PC m ⎧⋅=⎪⎨⋅=⎪⎩ 得111110,0,x z x y z -=⎧⎨+-=⎩令11x =，解得11z =，10y =．所以(1,0,1)m = ．·····································································································10分因此112cos ,2m AE m AE m AE ⋅===⋅ ．·······························································11分由图可知二面角B PC D --的大小为钝角．故二面角B PC D --的余弦值为12-．·········································································12分解法二：（1）同解法一．·····································································································6分（2）过点B 作BF 垂直于PC 于点F ，连接DF 、BD ．因为PB PD =，BC CD =，PC PC =，所以PBC PDC △≌△．······························································································7分因此易得090DFC BFC ∠=∠=，BF DF =．································································8分所以BFD ∠为二面角B PC D --的平面角．···································································9分设1PA AB ==，则BD =3BF DF ==．·························································10分在BDF △中，由余弦定理，得222222)133cos 2263BF DF BD BFD BF DF +-+-∠==-⋅．故二面角B PC D --的余弦值为12-．·········································································12分18．（12分）记n S 为数列{}n a 的前n 项和．已知0n a >，2634n n n S a a =+-．（1）求{}n a 的通项公式；（2）设2211n n n n n a a b a a +++=，求数列{}n b 的前n 项和n T ．【命题意图】本小题主要考查递推数列、等差数列的通项公式与数列求和等基础知识，考查推理论证能力与运算求解能力等，考查化归与转化思想、特殊与一般思想等，体现基础性，导向对发展逻辑推理、数学运算等核心素养的关注．【试题解析】解：（1）当1n =时，2111634S a a =+-，所以14a =或1-（不合，舍去）．································1分因为2634n n n S a a =+-①，所以当2≥n 时，2111634n n n S a a ---=+-②，由①-②得2211633n n n n n a a a a a --=+--，······································································2分所以()()1130n n n n a a a a --+--=．················································································3分又0n a >，所以13n n a a --=．······················································································4分因此{}n a 是首项为4，公差为3的等差数列．···································································5分故()43131n a n n =+-=+．························································································6分（2）由（1）得()()()()22313433231343134n n n b n n n n +++==+-++++，········································9分所以()33333392()2477103134434n n T n n n n n =+-+-+⋅⋅⋅+-=++++．····························12分19．（12分）ABC △中，60B =︒，2AB =，ABC △的面积为（1）求AC ；（2）若D 为BC 的中点，,E F 分别为,AB AC 边上的点（不包括端点），且120EDF ∠=︒，求DEF △面积的最小值．【命题意图】本小题主要考查解三角形、三角恒等变换等基础知识，考查推理论证能力和运算求解能力等，考查数形结合思想和化归与转化思想等，体现综合性与应用性，导向对发展直观想象、逻辑推理、数学运算及数学建模等核心素养的关注．【试题解析】解法一：（1）因为60B =︒，2AB =，所以1sin 2ABC S AB BC B =⋅⋅⋅△13222BC =⨯⨯32BC =，·············································2分又ABC S =△，所以4BC =．···················································································3分由余弦定理，得2222cos AC AB BC AB BC B =+-⋅⋅·······················································4分221242242=+-⨯⨯⨯12=，·························································································5分所以AC =········································································································6分（2）设BDE θ∠=，[]0,60θ∈︒︒，则60CDF θ∠=︒-．在BDE △中，由正弦定理，得sin sin BD DE BED B=∠，·························································7分即2sin(60)32θ=︒+，所以3sin(60)DE θ=︒+；···························································8分在CDF △中，由正弦定理，得sin sin CD DF CFD C =∠，由（1）可得30C =︒，即21sin(90)2DF θ=︒-，所以1cos DF θ=；·····································9分所以1sin 2DEF S DE DF EDF =⋅⋅⋅∠△34sin(60)cos θθ=︒+⋅=········································································10分=，············································································11分当15θ=︒时，sin(260)1θ+︒=，min ()6DEF S ==-△故DEF △面积的最小值为6-．············································································12分解法二：（1）同解法一．·····································································································6分（2）设CDF θ∠=，[]0,60θ∈︒︒，则60BDE θ∠=︒-．在CDF △中，由正弦定理，得sin sin CD DFCFD C=∠，························································7分由（1）可得30C =︒，即21sin(30)2DFθ=︒+，所以()1sin 30DF θ=︒+；···························8分在BDE △中，由正弦定理，得sin sin BD DEBED B=∠，即2sin(120)32θ=︒-，所以sin(120)DE θ=︒-；·························································9分所以1sin 2DEF S DE DF EDF =⋅⋅⋅∠△()334sin 30sin(120)θθ=⋅︒+⋅︒-13312222=⎝⎭⎝⎭ (10)分=······················································································11分当45θ=︒时，sin 21θ=，min ()6DEF S ==-△故DEF △面积的最小值为6-．············································································12分20．（12分）已知椭圆2222:1(0)x y E a b a b+=>>的离心率为12，点32A 在E 上．（1）求E 的方程；（2）斜率不为0的直线l 经过点1(,0)2B ，且与E 交于Q P ,两点，试问：是否存在定点C ，使得QCB PCB ∠=∠？若存在，求C 的坐标；若不存在，请说明理由．【命题意图】本小题主要考查椭圆的几何性质、直线与椭圆的位置关系等基础知识，考查推理论证能力、运算求解能力等，考查化归与转化思想、数形结合思想、函数与方程思想等，体现基础性、综合性与创新性，导向对发展逻辑推理、直观想象、数学运算、数学建模等核心素养的关注．【试题解析】解法一：（1）因为椭圆E的离心率12e a ==，所以2234a b =①，··································1分点)23,3(A 在椭圆上，所以143322=+ba ②，·······························································2分由①②解得42=a ，32=b ．························································································3分故E 的方程为13422=+y x ．··························································································4分（2）假设存在定点C ，使得PCB QCB ∠=∠．由对称性可知，点C 必在x 轴上，故可设(,0)C m ．··························································5分因为PCB QCB ∠=∠，所以直线PC 与直线QC 的倾斜角互补，因此0PC QC k k +=．·············6分设直线l 的方程为：21+=ty x ，),(11y x P ，),(22y x Q ．由221,2143x ty x y ⎧=+⎪⎪⎨⎪+=⎪⎩消去x ，得04512)1612(22=-++ty y t ，···············································7分2222(12)4(1216)(45)144180(1216)0t t t t ∆=-⨯+⨯-=+⨯+>，所以t ∈R ，122121216t y y t +=-+，122451216y y t =-+，····································································8分因为0=+QC PC k k ，所以02211=-+-mx y m x y ，所以0)()(1221=-+-m x y m x y ，即0)21()21(1221=-++-+m ty y m ty y ．·························9分整理得121212()()02ty y m y y +-+=，所以0161212)21()161245(222=+-⨯-++-⨯t t m t t ，即01612)12)(21(902=+--+-t t m t ．·················10分所以0)21(1290=-+m t t ，即0)]21(1290[=-+t m ，对t ∈R 恒成立，即0)1296(=-t m 对t ∈R 恒成立，所以8=m ．·····························································11分所以存在定点)0,8(C ，使得QCB PCB ∠=∠．·······························································12分解法二：（1）同解法一．·····································································································4分（2）若点C 存在，当直线PQ 垂直x 轴时，点C 必在x 轴上，如果直线PQ 不垂直x 轴，由对称性可知，点C 也必在x 轴上．···········································5分假设存在点)0,(m C ，使得QCB PCB ∠=∠，即直线PC 与直线QC 的倾斜角互补，所以0=+QC PC k k ．····································································································6分设直线l 的方程为)21(-=x k y ，),(11y x P ，),(22y x Q ．由221(2143y k x x y ⎧=-⎪⎪⎨⎪+=⎪⎩消去x ，得0124)34(2222=-+-+k x k x k ，··········································7分22222(4)4(43)(12)1801440k k k k ∆=--⨯+-=+>，所以k ∈R ，2122443k x x k +=+，34122221+-=k k x x ，··············································································8分因为0=+QC PC k k ，所以02211=-+-m x y m x y ，所以0)()(1221=-+-m x y m x y ，················9分即122111()()()022k x x m k x x m --+--=．整理得0]))(21(2[2121=+++-m x x m x x k ，··································································10分所以0]34421(34242[2222=++⨯+-+-m k k m k k k ，整理得0342432=+-⨯k m k ，对任意的k ∈R 恒成立，····························································11分所以8=m ，故存在x 轴上的定点)0,8(C ，使得QCB PCB ∠=∠．····································12分21．（12分）已知函数()2()1e xf x x ax =++．（1）讨论()f x 的单调性；（2）若函数()2()1e 1xg x x mx =+--在[)1,-+∞有两个零点，求m 的取值范围．【命题意图】本小题主要考查导数的综合应用，利用导数研究函数的单调性、最值和零点等问题，考查抽象概括、推理论证、运算求解能力，考查应用意识与创新意识，综合考查化归与转化思想、分类与整合思想、函数与方程思想、数形结合思想、有限与无限思想以及特殊与一般思想，考查数学抽象、逻辑推理、直观想象、数学运算、数学建模等核心素养．【试题解析】。