（2020新）北师大版三年级数学下册《21轴对称(一)》课件.ppt

1、轴对称（一）轴对称（一）（建议一课时完成）（建议一课时完成）三年级下册 二二 图形的运动图形的运动课后课后作业作业探索探索新知新知当堂当堂检测检测课堂课堂小结小结1课堂探究点课堂探究点2课时流程课时流程折一折，看一看。折一折，看一看。对称轴对称轴轴对称图形轴对称图形探究点探究点 认识轴对称图形和对称轴认识轴对称图形和对称轴1判断下面图形是不是轴对称图形，是的在括号里打判断下面图形是不是轴对称图形，是的在括号里打“”，不，不是的打是的打“”。小试牛刀小试牛刀（源于（源于典中点典中点）2给是轴对称图形的数字和字母涂上颜色。给是轴对称图形的数字和字母涂上颜色。给数字给数字3，8和字母和字母H，W涂上

2、颜色。涂上颜色。3填一填。填一填。(1)如果一个图形沿着一条直线对折，折痕两侧的部分能够如果一个图形沿着一条直线对折，折痕两侧的部分能够()，这个图形就叫作，这个图形就叫作()，折痕所，折痕所在的直线叫作在的直线叫作()。(2)在字母在字母A，B，C，E，F，M，Y，T，H中，可以看成中，可以看成轴对称图形的是轴对称图形的是()。完全重合完全重合对称轴对称轴轴对称图形轴对称图形A，B，C，E，M，Y，T，H4选择。选择。(将正确答案的字母填在括号里将正确答案的字母填在括号里)(1)下面不是轴对称图形的是下面不是轴对称图形的是()。(2)下列汉字中，可以看成是轴对称图形的是下列汉字中，可以看成是

3、轴对称图形的是()。A长长B禾禾C山山D上上(3)下面是几种汽车标志，其中不是轴对称图形的是下面是几种汽车标志，其中不是轴对称图形的是()。ACC5下面图形中的虚线是它们的对称轴吗？是的画下面图形中的虚线是它们的对称轴吗？是的画“”，不，不是的画是的画“”。轴对称图形沿着对称轴对折后，两侧能够完全重合，对轴对称图形沿着对称轴对折后，两侧能够完全重合，对称点到对称轴的距离相等。称点到对称轴的距离相等。归纳总结：归纳总结：（讲解源于（讲解源于点拨点拨）1利用附页利用附页1中图中图2折一折，看一看，下面哪些图形是轴折一折，看一看，下面哪些图形是轴对称图形？对称图形？夯实基础夯实基础（教材（教材P24

4、练一练）练一练）2下面哪些图形是轴对称图形？画下面哪些图形是轴对称图形？画“”。3找一找下列哪些数字、汉字、字母是轴对称图形。找一找下列哪些数字、汉字、字母是轴对称图形。4用对折的方法找出下面图形（附页用对折的方法找出下面图形（附页1中图中图3）的对称轴。）的对称轴。5生活中有许多图案都是轴对称的，请你找一找并和同伴说一说生活中有许多图案都是轴对称的，请你找一找并和同伴说一说。银杏树叶银杏树叶斜拉桥斜拉桥布依族的蜡染布依族的蜡染京剧脸谱京剧脸谱6判断：长方形是轴对称图形，有判断：长方形是轴对称图形，有4条对称轴，如下图。条对称轴，如下图。()易错辨析易错辨析（选题源于（选题源于典中点典中点）7

5、下图是轴对称图形吗？如果是，请画出它的对称轴。下图是轴对称图形吗？如果是，请画出它的对称轴。辨析：没有弄清轴对称图形的特征，误认为能分成两个大辨析：没有弄清轴对称图形的特征，误认为能分成两个大小一样的图形就一定是对称的。小一样的图形就一定是对称的。题图不是轴对称图形题图不是轴对称图形版权申明本文部分内容，包括文字、图片、以及设计等在网上搜集整理.版权为个人所有This article includes some parts,including text,pictures,and design.Copyright is personal ownership.用户可将本文地内容或服务用于个人学习、

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21、为个人所有This article includes some parts,including text,pictures,and design.Copyright is personal ownership.用户可将本文地内容或服务用于个人学习、研究或欣赏，以及其他非商业性或非盈利性用途，但同时应遵守著作权法及其他相关法律地规定，不得侵犯本网站及相关权利人地合法权利.除此以外，将本文任何内容或服务用于其他用途时，须征得本人及相关权利人地书面许可，并支付报酬.Users may use the contents or services of this article for personal

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23、service of this article is used for other purposes,written permission and remuneration shall be obtained from the person concerned and the relevant obligee.转载或引用本文内容必须是以新闻性或资料性公共免费信息为使用目地地合理、善意引用，不得对本文内容原意进行曲解、修改，并自负版权等法律责任.Reproduction or quotation of the content of this article must be reasonable

24、and good-faith citation for the use of news or informative public free information.It shall not misinterpret or modify the original intention of the content of this article,and shall bear legal liability such as copyright.版权申明本文部分内容，包括文字、图片、以及设计等在网上搜集整理.版权为个人所有This article includes some parts,includ

25、ing text,pictures,and design.Copyright is personal ownership.用户可将本文地内容或服务用于个人学习、研究或欣赏，以及其他非商业性或非盈利性用途，但同时应遵守著作权法及其他相关法律地规定，不得侵犯本网站及相关权利人地合法权利.除此以外，将本文任何内容或服务用于其他用途时，须征得本人及相关权利人地书面许可，并支付报酬.Users may use the contents or services of this article for personal study,research or appreciation,and other non

26、-commercial or non-profit purposes,but at the same time,they shall abide by the provisions of copyright law and other relevant laws,and shall not infringe upon the legitimate rights of this website and its relevant obligees.In addition,when any content or service of this article is used for other pu

27、rposes,written permission and remuneration shall be obtained from the person concerned and the relevant obligee.转载或引用本文内容必须是以新闻性或资料性公共免费信息为使用目地地合理、善意引用，不得对本文内容原意进行曲解、修改，并自负版权等法律责任.Reproduction or quotation of the content of this article must be reasonable and good-faith citation for the use of news

28、or informative public free information.It shall not misinterpret or modify the original intention of the content of this article,and shall bear legal liability such as copyright.版权申明本文部分内容，包括文字、图片、以及设计等在网上搜集整理.版权为个人所有This article includes some parts,including text,pictures,and design.Copyright is pe

29、rsonal ownership.用户可将本文地内容或服务用于个人学习、研究或欣赏，以及其他非商业性或非盈利性用途，但同时应遵守著作权法及其他相关法律地规定，不得侵犯本网站及相关权利人地合法权利.除此以外，将本文任何内容或服务用于其他用途时，须征得本人及相关权利人地书面许可，并支付报酬.Users may use the contents or services of this article for personal study,research or appreciation,and other non-commercial or non-profit purposes,but at th

30、e same time,they shall abide by the provisions of copyright law and other relevant laws,and shall not infringe upon the legitimate rights of this website and its relevant obligees.In addition,when any content or service of this article is used for other purposes,written permission and remuneration s

31、hall be obtained from the person concerned and the relevant obligee.转载或引用本文内容必须是以新闻性或资料性公共免费信息为使用目地地合理、善意引用，不得对本文内容原意进行曲解、修改，并自负版权等法律责任.Reproduction or quotation of the content of this article must be reasonable and good-faith citation for the use of news or informative public free information.It shall not misinterpret or modify the original intention of the content of this article,and shall bear legal liability such as copyright.