7. How can you expect to be successful ___ you won’t listen in class ?
A. in case B. when C. unless D. even if
6. Doing your homework is a sure way to improve your test scores , and this is especially true ___ it comes to classroom tests .
A. before B. since C. when D. after
5. To keep healthy , most retired old people ___ jogging as a regular form of exercise .
A. take up B. make up C. carry out D. hold out
4. It is not so difficult to learn program well. ___ you need is patience and persistence .
A. Something B. All C. Both D. Everything
3. --Will you be ___ this afternoon , John ?
--It depends. I’m afraid I’ll be called in by my manager.
A. suitable B. convenient C. accurate D. available
2. After the long journey , the Smiths returned home , ____ .
A. safe but tired B. safely but tired C. safe and tiring D. safely and tiring
第一节:单项填空(共20小题:每小题0.5分,满分10分)
从A、B、C、D四个选项中,选出可以填入空白处的最佳选项,并在答题卡上将该选项标号涂黑。
1. In ___ preparation for the launching of Chang’e I , scientists need ___ knowledge of weather changes .
A. the ; the B. a ; / C. / ; a D. the ; a
教学环节 |
教学内容 |
师生互动 |
设计意图 |
提出问题![]() |
示例1:数集的拓展![]() 示例2:方程(x – 2) (x2 – 3) = 0的解集. ①在有理数范围内,②在实数范围内. |
学生思考讨论.![]() |
挖掘旧知,导入新知,激发学习兴趣. |
形成概念 |
1.全集的定义.![]() 如果一个集合含有我们所研究问题中涉及的所有元素,称这个集合为全集,记作U. ![]() 示例3:A = {全班参加数学兴趣小组的同学},B = {全班设有参加数学兴趣小组的同学},U = {全班同学},问U、A、B三个集关系如何. ![]() 2.补集的定义 ![]() 补集:对于一个集合A,由全集U中不属于集合A的所有元素组成的集合称为集合A相对于全集U的补集,记作 ![]() ![]() 即 ![]() ![]() ![]() Venn图表示 ![]() ![]() ![]() |
师:教学学科中许多时候,许 多问题都是在某一范围内进行研究. 如实例1是在实数集范围内不断扩大数集. 实例2:①在有理数范围内求解;②在实数范围内求解. 类似这些给定的集合就是全集.![]() 师生合作,分析示例 ![]() 生:①U = A∪B, ![]() ②U中元素减去A中元素就构成B. ![]() 师:类似②这种运算得到的集合B称为集合A的补集,生师合作交流探究补集的概念. |
合作交流,探究新知,了解全集、补集的含义. |
应用举例![]() 深化概念 |
例1 设U = {x | x是小于9的正整数},A = {1,2,3},B = {3,4,5,6},求![]() ![]() ![]() 例2 设全集U = {x | x是三角形},A = {x|x是锐角三角形},B = {x | x是钝角三角形}. 求A∩B, ![]() |
学生先尝试求解,老师指导、点评.![]() 例1解:根据题意可知,U = {1,2,3,4,5,6,7,8},所以 ![]() ![]() ![]() ![]() 例2解:根据三角形的分类可知 A∩B = ![]() ![]() A∪B = {x | x是锐角三角形或钝角三角形}, ![]() ![]() |
加深对补集概念的理解,初步学会求集合的补集. |
性质探究 |
补集的性质:![]() ①A∪( ![]() ![]() ②A∩( ![]() ![]() ![]() 练习1:已知全集U = {1, 2, 3, 4, 5, 6, 7},A={2, 4, 5},B = {1, 3, 5, 7},求A∩( ![]() ![]() ![]() ![]() 总结: ![]() ( ![]() ![]() ![]() ![]() ( ![]() ![]() ![]() |
师:提出问题![]() 生:合作交流,探讨 ![]() 师生:学生说明性质①、②成立的理由,老师点评、阐述. ![]() 师:变式练习:求A∪B,求 ![]() ![]() ![]() ![]() 解:因为 ![]() ![]() ![]() ![]() ( ![]() ![]() ![]() ![]() |
能力提升. 探究补集的性质,提高学生的归纳能力. |
应用举例 |
例2 填空![]() (1)若S = {2,3,4},A = {4,3},则 ![]() ![]() (2)若S = {三角形},B = {锐角三角形},则 ![]() ![]() (3)若S = {1,2,4,8},A = ![]() ![]() ![]() (4)若U = {1,3,a2 + 3a + 1},A = {1,3}, ![]() ![]() (5)已知A = {0,2,4}, ![]() ![]() ![]() . ![]() (6)设全集U = {2,3,m2 + 2m – 3},A = {|m + 1| ,2}, ![]() ![]() (7)设全集U = {1,2,3,4},A = {x | x2 – 5x + m = 0,x∈U},求 ![]() ![]() |
师生合作分析例题.![]() 例2(1):主要是比较A及S的区别,从而求 ![]() 例2(2):由三角形的分类找B的补集. 例2(3):运用空集的定义. 例2(4):利用集合元素的特征. 综合应用并集、补集知识求解. 例2(7):解答过程中渗透分类讨论思想. 例2(1)解: ![]() 例2(2)解: ![]() 例2(3)解: ![]() 例2(4)解:a2 + 3a + 1 = 5, a = – 4或1. 例2(5)解:利用韦恩图由A设 ![]() 例2(6)解:由题m2 + 2m – 3 = 5且|m + 1| = 3, 解之m = – 4或m = 2. 例2(7)解:将x = 1、2、3、4代入x2 – 5x + m = 0中,m = 4或m = 6, 当m = 4时,x2 – 5x + 4 = 0,即A = {1,4}, 又当m = 6时,x2 – 5x + 6 = 0,即A = {2,3}. 故满足条件: ![]() ![]() |
进一步深化理解补集的概念. 掌握补集的求法. |
归纳总结 |
1.全集的概念,补集的概念. 2. ![]() ![]() 3.补集的性质: ①( ![]() ![]() ![]() ② ![]() ![]() ![]() ![]() ③( ![]() ![]() ![]() ( ![]() ![]() ![]() |
师生合作交流,共同归纳、总结,逐步完善. |
引导学生自我回顾、反思、归纳、总结,形成知识体系. |
课后作业 |
1.1 第四课时习案 |
学生独立完成 |
巩固基础、提升能力 |
备选例题
例1 已知A = {0,2,4,6},SA = {–1,–3,1,3},
SB = {–1,0,2},用列举法写出集合B.
[解析]∵A = {0,2,4,6},SA = {–1,–3,1,3},
∴S = {–3,–1,0,1,2,3,4,6}
而SB = {–1,0,2},∴B =
S (
SB) = {–3,1,3,4,6}.
例2 已知全集S = {1,3,x3 +
3x2 + 2x},A = {1,|2x – 1|},如果SA = {0},则这样的实数x是否存在?若存在,求出x;若不存在,请说明理由.
[解析]∵SA = {0},∴0∈S,但0
A,∴x3 +
3x2 + 2x = 0,x(x + 1) (x + 2) = 0,
即x1 = 0,x2 = –1,x3 = –2.
当x = 0时,|2x – 1| = 1,A中已有元素1,不满足集合的性质;
当x= –1时,|2x – 1| = 3,3∈S; 当x = –2时,|2x – 1| = 5,但5S.
∴实数x的值存在,它只能是–1.
例3 已知集合S = {x | 1<x≤7},A = {x | 2≤x<5},B = {x | 3≤x<7}. 求:
(1)(SA)∩(
SB);(2)
S (A∪B);(3)(
SA)∪(
SB);(4)
S (A∩B).
[解析]如图所示,可得
A∩B = {x | 3≤x<5},A∪B = {x | 2≤x<7},
SA = {x | 1<x<2,或5≤x≤7},
SB = {x | 1<x<3}∪{7}.
由此可得:(1)(SA)∩(
SB) = {x | 1<x<2}∪{7};
(2)S (A∪B) = {x | 1<x<2}∪{7};
(3)(SA)∪(
SB) = {x | 1<x<3}∪{x |5≤x≤7} = {x | 1<x<3,或5≤x≤7};
(4)S (A∩B) = {x | 1<x<3}∪{x | 5≤x≤7} = {x | 1<x<3,或5≤x≤7}.
例4 若集合S = {小于10的正整数},,
,且(
SA)∩B = {1,9},A∩B = {2},(
SA)∩(
SB) = {4,6,8},求A和B.
[解析]由(SA)∩B = {1,9}可知1,9
A,但1,9∈B,
由A∩B = {2}知,2∈A,2∈B.
由(SA)∩(
SB) = {4,6,8}知4,6,8
A,且4,6,8
B
下列考虑3,5,7是否在A,B中:
若3∈B,则因3A∩B,得3
A.
于是3∈
SA,所以3∈(
SA)∩B,
这与(SA)∩B = {1,9}相矛盾.
故3B,即3∈(
SB),又∵3
(
SA)∩(
SB),
∴3(
SA),从而3∈A;同理可得:5∈A,5
B;7∈A,7
B.
故A = {2,3,5,7},B = {1,2,9}.
评注:此题Venn图求解更易.
通过示例,尝试发现式学习法;通过示例的分析、探究,培养发现探索一般性规律的能力.
重点:补集概念的理解;难点:有关补集的综合运算.
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