2022年多边形教学设计2 .pdf

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1、16.1 多边形一、教材分析本节内容是在第一学期学完三角形基础上进一步学习的，是三角形内角和公式的延伸与拓展。内容分三部分：（1）多边形的有关概念（2）多边形内角和公式的探索（3）多边形内角和公式的简单运用，其中多边形内角和公式的推导既是重点又是难点。教学时应注意引导学生合理分割多边形，将它转化为若干个三角形或三角形和四边形的组合，用这些熟悉图形的知识和性质来解决多边形的问题。二、学情分析因为有三角形的知识作基础，所以学生通过教师的引导和自己的努力可以探究出多边形的内角和；但对于“转化思想”，学生缺少这种思想，学生基础也不够好，对学生个体而言，思维的广阔性和发散性也肯定不够。三、设计理念创设问

2、题情境，感受生活中的数学；设计开放性的问题及问题串，培养学生的问题意识，激起学生的主动探索；组织探究，让学生体会转化思想的魅力；同时加强师生、生生间的合作交流，培养学生积极思考的精神，让不同的学生在数学上得到不同的发展。四、教具：尺子、自制四边形教具五、设计说明1本节分成三课时分别介绍教学目标、教学过程。本课设计时我努力要求自己真正成为教学的组织者、引导者，努力为学生营造良好的学习氛围，让学生在一个充满问题的氛围中探索求知，设计一系列的问题串，以激活学生的思维，变“要我学”为“我要学”，让学生带着问题进课堂，最后带着新问题走出课堂，更有利于发挥学生的学习积极性、主动性与创造性。2探究时要努力调

3、动起学生探究的意识，并给予学生时间和空间，通过自主和合作让思维碰撞，从而产生出各种思维，进行充满激情的学习活动。同时适时运用鼓励、表扬与引导，让学生的探究与研究得到升华。通过数学课，也想让学生明白：数学的奥秘很深，你若不研究它，会感到无比枯燥：你若研究它，则会觉得趣味无穷，这样才能真正体验学习数学的快乐。16.1.1多边形一、教学目标：1了解多边形、正多边形、多边形的对角线、内角和、外角和等概念；初步掌握多边形内角和公式，会运用多边形内角和进行相关计算。2经历把多边形内角和问题转化为三角形内角和问题的过程，体会转化思想在几何中的应用，同时体会从特殊到一般的认识问题的方法；3、通过猜想探究等数学

4、活动培养学生学习数学的方法，感受数学充满着探索，提高学生学习数学的热情；通过师生合作，生生合作体验合作的快乐和学习数学的快乐。二、教学重点：探索和运用。三、教学难点：多边形内角和公式的探索。教学关键：应用化归的数学方法,把多边形问题转化为三角形问题来解决.四、教学方法：探究与互动五、教学过程：（一）引入1前面我们学习了三角形，知道了由三条线段首尾顺次相接组成的平面图形叫三角形，它有三个内角，三条边，也称三边形。2、你知道什么是四边形吗？什么是五边形呢？什么是n 边形呢？（设计意图：通过与三角形类比进行知识的迁移，引出本节课标题与多边形的概念。）（二）新课1、多边形概念：由 n 条线段首尾顺次相

5、接组成的平面图形叫n 边形，也叫多边形。2、动手画一画：请同学们动手画四边形、五边形、六边形，然后相互评价。（教师投影学生作品，说明多边形的边、顶点、内角、外角等的含义与三角形的相同。多边形的表示方法：我们常把表示多边形各个顶点的字母顺次排列在一起，表示这个多边形。如下图：四边形ABCD，五边形 ABCDE DCBAEDCBA我们只研究凸多边形，若出现凹多边形则进行说明凸多边形：把多边形的任何一边向两个方向延长，如果其他各边都在延长所得直线的同一旁，这样的多边形叫凸多边形。凹多边形：如果其他各边不是都在延长所得直线的同一旁，这样的多边形叫凹多边形。DCBA凹四边形（设计意图：说明知识间的联系，

6、有利于学生的知识体系的形成。）多边形分类：凸多边形和凹多边形。3有各边都相等、各角都相等的三角形和四边形吗？（引出正多边形的概念。）文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7

7、H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8

8、S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7

9、H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8

10、S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7

11、H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8

12、S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8正多边形概念：各条边都相等，各个角都相等的多边形叫正多边形4你能举一些生活中的多边形的实例吗？设计意图：感悟数学图形，揭示数学从生活中来。5、三角形具有稳定性，边数大于3 的多边形具有稳定性吗？、(先让学生猜测，教师再以四边形为

13、例用教具进行验证)问题：你知道这个知识在生活中的应用吗？追问：若要把这个四边形稳定下来，你有什么办法吗？（设计意图：又是一个开放性的问题，通过这个问题引出对角线的概念）对角线的概念：联结多边形不相邻的两个顶点的线段叫做多边形的对角线填表：(内角和先不填)多边形图形边数顶点个数内角个数外角个数从一顶点出发可引出对角线的条数分成的三角形的个数内角和三角形3 四边形4 五边形5 六边形6 七边形7 n 边形n 过一个顶点的对角线可将多边形划分成若干个三角形，这是我们熟悉的图形，这样我们就可以通过研究三角形来研究多边形了，这就是数学上的转化思想。（设计意图：通过问题串让学生了解四边形的不稳定性，加深对

14、对角线的认识，并为下面的转化，多边形内角和的求法做准备。）6、多边形内角和的求法：小明、小亮分别利用下面的图形求出了该五边形的五个内角的和，你知道他们是怎样做的吗？请你发表你的意见。文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A

15、4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3

16、ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A

17、4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3

18、ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A

19、4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3

20、ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8小明180180180?180 180180 180 180 小亮小明：五边形的内角和为1803=540小亮：五边形的内角和为1805360=540（设计意图：创设这个问题情境是

21、为了让学生实现“跳一跳可以摘到果子”，从五边形入手，有利于学生探求它与三角形或四边形的关系，教师渗透转化思想。）问题 7：你还有其他方法吗?和你的同伴交流。（教师关注：学生能否找到不同的分割方法，实现转化）各个小组想出的方法，师生一一分析与点评，教师要灵活应答。主要方法参考：1还可以在一边上取一点和五个顶点连接，形成4 个三角形，故内角和为4180-180=5402点还可以取在外部，故内角和为4180-180=5403连一条对角线，把五边形分成一个三角形和一个四边形，内角和为180+360=540；问题：比较一下，这些方法中你们觉得哪种方法最简单？设计意图：方法多了，归纳一下有助于学生的思维清

22、晰起来，最终寻找到最佳方案，真正认识转化思想。现在，我们会通过各种方法求五边形的内角和了，相信大家能从这里体会到转化思想的魅力了,也能灵活运用了。那么你能继续探索出n 边形的内角和吗？继续填表（内角和），总结出多边形内角和：(n-2)180(三)多边形的内角和(n-2)180的简单应用问题 1：知道了多边形的内角和公式，咱们能解决哪些问题呢？（已知 n 边形的边数，可以求它的内角和；已知 n 边形的内角和，可以求它的边数。）设计意图：让学生对所学知识的用处做一个理性的归纳，明确它的应用。1十边形的内角和的度数为_ 2求下列图形中的x 的度数。2xx1501207580120 x3、若一个四边形

23、的四个角之比为1：2：3：4，则它的角分别为。4、已知一个多边形的内角和为1080,则它的边数为 _ _（四）、课堂小结文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8

24、文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6

25、S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8

26、文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6

27、S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8

28、文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6

29、S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8本课你的收获是 _；本课你最感兴趣的是 _；你还想进一步研究的是 _。（设计意图：培养学生善于小结和归纳的习惯，通过这三个设问，使学生对今天的知识有更理性的归纳；实现带着问题走进课堂，带着新问题走出课堂的理念。）（五）、作业：书 p49 练

30、习 1 A 组 1 16.1.2多边形的内角和与外角和一、教学目标：1、巩固练习多边形内角和，推导外角和定理，灵活应用内角和与外角和进行计算。2、经历探究多边形外角和计算方法的过程，培养学生的合作交流意识。3、让学生在观察、合作、讨论、交流中感受数学转化思想和实际应用价值，同时培养学生善于发现、积极思考、合作学习、勇于创新的学习态度。二、教学重点：多边形的内角和与外角和的应用三、教学难点：多边形的内角和与外角和的应用四、教学方法：讲练结合五、教学过程：（一）复习1、多边形内角和如何求？2、练习：求出八边形的内角和？正十二边形的每一个内角是多少度？（二）新课1、在四边形 ABCD 中，1，2，3

31、，4 是四个外角，怎样求出它们的和呢？（引出本节课外角和概念）外角和：多边形的每个顶点处各取一个外角之和。4321DCBA分析：1+ACD=180，2+ADC=180，3+DAB=180，4+ABC=1801+2+3+4=(180 ACD)+(180 ADC)+(180 DAB)+(180 ABC)=720（ACD+ADC+DAB+ABC）=720360=360那么五边形呢？n边形呢？2、多边形的外角和：学生用上述同样的方法求出五边形的外角和（学生展示）n 边形的外角和：文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5

32、I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档

33、编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5

34、I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档

35、编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5

36、I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档

37、编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5

38、I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8180n180(n2)=180n180n+360=360结论：多边形的外角和3603、例题例 1、已知一个多边形的内角和是2340，求这个多边形的边数例 2、已知一个多边形每个外角都是20，求这个多边形的内角和例 3、已知一个多边形每个内角都是135，求这个多边形的边数例 4、如果一个多边形的每个内角都相等，它的一个外角等于一个内角的三分之二，求这个多边形的边数。4、练习分层测试卡 p46A 组 二、三思考：正 n 边形的每一个外角都不大于40，则满足条件的多边形边数最少是（）A

39、、七边形B、八边形C、九边形D、十边形（三）总结本课你的收获是 _；本课你最感兴趣的是 _；你还想进一步研究的是 _。（四）作业数学书 p49 A 组 2、3 分层测试卡 P47 B 组二、三16.1.3多边形的内角和与外角和（练习）一、教学目标：1、继续巩固练习多边形内角和与外角和知识点，灵活应用内角和与外角和进行计算。2、经历计算、推理的过程，培养学生的计算与合作交流意识。3、培养学生积极思考、逻辑推理能力。二、教学重点：多边形的内角和与外角和的应用三、教学难点：多边形的内角和与外角和的应用四、教学方法：讲练结合五、教学过程：（一）复习1、多边形内角和？2、多边形外角和？（二）练习1、在四

40、边形 ABCD 中，ABBC 于 B，ADDC 于 D，点 E 在 BA 的延长线上求证：DAE=C 文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A

41、4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3

42、ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A

43、4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3

44、ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A

45、4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3

46、ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8EDCBA2、正五边形 ABCDE，从点 A 作对角线 AC,AD 问：（1）图中有几个等腰三角形吗？（2）ACD 是等腰三角形码？说明理由EDCBA3、如图：A+B+C+D+E+F=FEDCBA分析：构造一个四边形，联结BE，再运用三角形外角性质1 就可以

47、求出FEDCBAC+D=CBE+DEB A+ABC+C+D+DEF+F=A+ABC+CBE+DEB+DEF+F=A+ABE+BEF+F=360思考：把纸片 ABC 沿 DE 对折，如图，则 A 与1+2 的关系（）文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I

48、7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z

49、8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I

50、7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z8S3 HS6S5I2F4D3 ZZ3I7H6X5A8文档编码:CF5A4P3Z