基本不等式教学设计

relationship, established equivalent relationship 14, and subject: application problem (4)--scores and percentage application problem review content overview answers scores, and percentage application preliminary knowleoblem of key is: according to meaniphing, (1) determine standard volume (units \ionship, Then in-line solution. Category fraction multiplication word problem score Division applications engineering problem problem XV, a subject: review of the measurement of the amount of capacity, measurement and units of measurement of comnt and their significance in rate 1, currency, length, area, volume, unit size, volume, weight and rate. (Omitted) 2, commonly used time units and their relationships. (Slightly) with a measurement units Zhijian of of poly 1, and of method 2, and poly method 3, and of method and poly method of relationship measurement distance of method 1, and tool measurement 2, and estimates 16, and subject: geometry preliminary knowledge (1)--line and angle review content line, and segment, and Ray, and vertical, and parallel, and angle angle of classification (slightly) 17, and subject: geometry prdge (2)--plane gracs review content triangle, and edges shaped, and round, and fan axisymmetric graphics perimeter and area combination graphics of area subject : Preliminary knowledge (3)-review of solid content category 1-d shapes are divided into: cylinder and cone 2, column is divided into: cuboid, square 3, cone cone of the features of cuboids and cubes relatimon units of measuremeonship between characteristics of circular cone is slightly solid surface area and volume 1, size 2, table ...和3.4.1基本不等式

教材分析

本节课是在系统的学习了不等关系和不等式性质，掌握了不等式性质的基础上展开的，作为重要的基本不等式之一,为后续的学习奠定基础。 要进一步了解不等式的性质及运用，研究最值问题，此时基本不等式是必不可缺的。基本不等式在知识体系中起了承上启下的作用，同时在生活及生产实际中有着广泛的应用，因此它也是对学生进行情感价值观教育的好素材，所以基本不等式应重点研究。

教学中注意用新课程理念处理教材，学生的数学学习活动不仅要接受、记忆、模仿和练习，而且要自主探索、动手实践、合作交流、阅读自学，师生互动，教师发挥组织者、引导者、合作者的作用，引导学生主体参与、揭示本质、经历过程。

就知识的应用价值上来看，基本不等式是从大量数学问题和现实问题中抽象出来的一个模型，在公式推导中所蕴涵的数学思想方法如数形结合、归纳猜想、演绎推理、分析法证明等在各种不等式研究问题中有着广泛的应用；另外它在如“求面积一定，周长最小；周长一定，面积最大”等实际问题的计算中也经常涉及到。

就内容的人文价值上来看，基本不等式的探究与推导需要学生观察、分析、归纳、猜想，有助于培养学生的创新思维和探索精神,是培养学生应用意识和数学能力的良好载体。

课程目标分析

依据《新课程标准》对《不等式》学段的目标要求和学生的实际情况，特确定如下目标：

1、知识与能力目标：理解掌握基本不等式，并能运用基本不等式解决一些简单

的求最值问题；理解算数平均数与几何平均数的概念，学会构造条件使用基本不等式；培养学生探究能力以及分析问题解决问题的能力。

2、过程与方法目标：按照创设情景，提出问题→ 剖析归纳证明→ 几何解释→ 应

用（最值的求法、实际问题的解决）的过程呈现。启动观察、分析、归纳、总结、抽象概括等思维活动，培养学生的思维能力，体会数学概念的学习方法，通过运用多媒体的教学手段，引领学生主动探索基本不等式性质，体会学习数学规律

relationship, established equivalent relationship 14, and subject: application problem (4)--scores and percentage application problem review content overview answers scores, and percentage application preliminary knowleoblem of key is: according to meaniphing, (1) determine standard volume (units \n in-line solution. Category fraction multiplication word problem score Division applications engineering problem problem XV, a subject: review of the measurement of the amount of capacity, measurement and units of measurement of com measurement and their significance in rate 1, currency, length, area, volume, unit size, volume, weight and rate. (Omitted) 2, commonly used time units and their relationships. (Slightly) with a measurement units Zhijian of of poly 1, and of method 2, and poly method 3, and of method and poly method of relationship measurement distance of method 1, and tool measurement 2, and estimates 16, and subject: geometry preliminary knowledge (1)--line and angle review content line, and segment, and Ray, and vertical, and parallel, and angle angle of classification (slightly) 17, and subject: geometry prdge (2)--plane gracs review content triangle, and edges shaped, and round, and fan axisymmetric graphics perimeter and arehea combination graphics of area subject : Preliminary knowledge (3)-review of solid content category 1-d shapes are divided into: cylinder and cone 2, column is divided into: cuboid, square 3, cone cone of the features of cuboids and cubes relatimon units ofonship between characteristics of circular cone is slightly solid surface area and volume 1, size 2, table ...和的方法，体验成功的乐趣。

3、情感与态度目标：通过问题情境的设置，使学生认识到数学是从实际中来，

培养学生用数学的眼光看世界，通过数学思维认知世界，从而培养学生善于思考、勤于动手的良好品质。

教学重、难点分析

重点：应用数形结合的思想理解基本不等式，并从不同角度探索基本不等式

ab?a?b的证明过程及应用。 2难点：1、基本不等式成立时的三个限制条件（简称一正、二定、三相等）；

2、利用基本不等式求解实际问题中的最大值和最小值。

教法分析

本节课采用观察——感知——抽象——归纳——探究；启发诱导、讲练结合的教学方法，以学生为主体，以基本不等式为主线，从实际问题出发，放手让学生探究思索。以现代信息技术多媒体课件作为教学辅助手段，加深学生对基本不等式的理解。

教学准备

多媒体课件、板书

教学过程

教学过程设计以问题为中心，以探究解决问题的方法为主线展开。这种安排强调过程，符合学生的认知规律，使数学教学过程成为学生对知识的再创造、再发现的过程，从而培养学生的创新意识。 具体过程安排如下：

一、 创设情景，提出问题；

设计意图：数学教育必须基于学生的“数学现实”，现实情境问题是数学教学的平台，数学教师的任务之

relationship, established equivalent relationship 14, and subject: application problem (4)--scores and percentage application problem review content overview answers scores, and percentage application problem of key is: according to meaning, (1) determine standard volume (units \hen in-line solution. Category fraction multiplication word problem score Division applications engineering problem problem XV, a subject: review of the measurement of the amount of capacity, measurement and units of measurement of common units of measurement and their significance in rate 1, currency, length, area, volume, unit size, volume, weight and rate. (Omitted) 2, commonly used time units and their relationships. (Slightly) with a measurement units Zhijian of of poly 1, and of method 2, and poly method 3, and of method and poly method of relationship measurement distance of method 1, and tool measurement 2, and estimates 16, and subject: geometry preliminary knowledge (1)--line and angle review content line, and segment, and Ray, and vertical, and parallel, and angle angle of classification (slightly) 17, and subject: geometry preliminary knowledge (2)--plane graphics review content triangle, and edges shaped, and round, and fan axisymmetric graphics perimeter and area combination graphics of area subject : Preliminary knowledge (3)-review of solid content category 1-d shapes are divided into: cylinder and cone 2, column is divided into: cuboid, square 3, cone cone of the features of cuboids and cubes relationship between characteristics of circular cone is slightly solid surface area and volume 1, size 2, table ...和《基本不等式》教学设计

一就是帮助学生构造数学现实，并在此基础上发展他们的数学现实．基于此,设置如下情境:

上图是在北京召开的第24届国际数学家大会的会标，会标是根据中国古代数学家赵爽的弦图设计的，颜色的明暗使它看上去像一个风车，代表中国人民热情好客。

[问]你能在这个图中找出一些相等关系或不等关系吗？

本背景意图在于利用图中相关面积间存在的数量关系，抽象出不等式

a2?b2?2ab。在此基础上，引导学生认识基本不等式。

二、抽象归纳：

一般地，对于任意实数a,b，有a2?b2?2ab，当且仅当a＝b时，等号成立。 [问] 你能给出它的证明吗？ 学生在黑板上板书。

特别地，当a>0,b>0时，在不等式a2?b2?2ab中，以a、b分别代替a、b，得到什么？

设计依据：类比是学习数学的一种重要方法，此环节不仅让学生理解了基本不等式不等式的来源，突破了重点和难点，而且感受了其中的函数思想，为今后学习奠定基础. 答案：

ab?a?b(a,b?0)。 2【归纳总结】

如果a,b都是正数，那么ab?a?b，当且仅当a=b时，等号成立。 2a?b称为a,b的算术平均数，ab称2我们称此不等式为基本不等式。 其中为a,b的几何平均数。

三、理解升华：

relationship, established equivalent relationship 14, and subject: application problem (4)--scores and percentage application problem review content overview answers scores, and percentage application preliminary knowleoblem of key is: according to meaniphing, (1) determine standard volume (units \n in-line solution. Category fraction multiplication word problem score Division applications engineering problem problem XV, a subject: review of the measurement of the amount of capacity, measurement and units of measurement of com measurement and their significance in rate 1, currency, length, area, volume, unit size, volume, weight and rate. (Omitted) 2, commonly used time units and their relationships. (Slightly) with a measurement units Zhijian of of poly 1, and of method 2, and poly method 3, and of method and poly method of relationship measurement distance of method 1, and tool measurement 2, and estimates 16, and subject: geometry preliminary knowledge (1)--line and angle review content line, and segment, and Ray, and vertical, and parallel, and angle angle of classification (slightly) 17, and subject: geometry prdge (2)--plane gracs review content triangle, and edges shaped, and round, and fan axisymmetric graphics perimeter and arehea combination graphics of area subject : Preliminary knowledge (3)-review of solid content category 1-d shapes are divided into: cylinder and cone 2, column is divided into: cuboid, square 3, cone cone of the features of cuboids and cubes relatimon units ofonship between characteristics of circular cone is slightly solid surface area and volume 1, size 2, table ...和1、文字语言叙述：

两个正数的算术平均数不小于它们的几何平均数。 2、联想数列的知识理解基本不等式

已知a,b是正数，A是a,b的等差中项，G是a,b的正的等比中项，A与G有无确定的大小关系？

两个正数的等差中项不小于它们正的等比中项。 3、符号语言叙述： 若a?0,b?0，则有ab?a?ba?b，当且仅当a=b时，ab?。 22[问] 怎样理解“当且仅当”？（学生小组讨论，交流看法，师生总结）

“当且仅当a=b时，等号成立”的含义是：

当a=b时，取等号，即a?b?ab?a?b； 2仅当a=b时，取等号，即ab?4、探究基本不等式证明方法： [问] 如何证明基本不等式？

a?b?a?b。 2（意图在于引领学生从感性认识基本不等式到理性证明，实现从感性认识到理性认识的升华，前面是从几何图形中的面积关系获得不等式的，下面用代数的思想，利用不等式的性质直接推导这个不等式。）

2(a?b)?0展开证明。 方法一：作差比较或由

方法二：分析法（完成课本填空）

设计依据：课本是学生了解世界的窗口和工具，所以，课本必须成为学生赖以学会学习的文本.在教学中要让学生学会认真看书、用心思考，养成讲讲议议、动手动笔、仔细观察、用心体会的好习惯，真正学会读“数学书”。 要证

a?b?ab ① 2只要证a?b? ②

relationship, established equivalent relationship 14, and subject: application problem (4)--scores and percentage application problem review content overview answers scores, and percentage application problem of key is: according to meaning, (1) determine standard volume (units \hen in-line solution. Category fraction multiplication word problem score Division applications engineering problem problem XV, a subject: review of the measurement of the amount of capacity, measurement and units of measurement of common units of measurement and their significance in rate 1, currency, length, area, volume, unit size, volume, weight and rate. (Omitted) 2, commonly used time units and their relationships. (Slightly) with a measurement units Zhijian of of poly 1, and of method 2, and poly method 3, and of method and poly method of relationship measurement distance of method 1, and tool measurement 2, and estimates 16, and subject: geometry preliminary knowledge (1)--line and angle review content line, and segment, and Ray, and vertical, and parallel, and angle angle of classification (slightly) 17, and subject: geometry preliminary knowledge (2)--plane graphics review content triangle, and edges shaped, and round, and fan axisymmetric graphics perimeter and area combination graphics of area subject : Preliminary knowledge (3)-review of solid content category 1-d shapes are divided into: cylinder and cone 2, column is divided into: cuboid, square 3, cone cone of the features of cuboids and cubes relationship between characteristics of circular cone is slightly solid surface area and volume 1, size 2, table ...和《基本不等式》教学设计

要证②,只要证a?b? ?0 ③ 要证③,只要证(?)2?0 ④

显然, ④是成立的。当且仅当a=b时, ④中的等号成立 。

点评：证明方法叫做分析法,实际上是寻找结论的充分条件,执果索因的一种思维方法.

5、探究基本不等式的几何意义：借助初中阶段学生熟知的几何图形，引导学生

ab?a?b(a,b?0)2的几何解释，通过数形结合，赋予不等式

探究不等式

ab?a?b(a,b?0)2几何直观。进一步领悟不等式中等号成立的条件。

如图：AB是圆的直径，点C是AB上一点，CD⊥AB，AC=a,CB=b，CD

D?ab

aba?b2abOCAB几何解释实质可认为是：在同一半圆中，半径不小于半弦（直径是最长的弦）；或者认为是，直角三角形斜边的一半不小于斜边上的高。

四、探究归纳

下列命题中正确的是

①对于任意实数a,b，均有a?b?2ab；

②当x?0时，由于1?x2?2x，当且仅当1?x2时，即x=1时，等号成立。所以函数y?1?x2(x?0)的最小值为2；

π4π4?4；所以函数y?sinx?③当x?(0,)时，有sinx?在(0,)的最小

2sinx2sinx

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