2021年青岛版三年级数学下册第二单元对称.pdf

读书破万卷下笔如有神青岛版三年级数学下册第二单元对称教案教学内容：教科书第 19-21 页，认识对称现象教学目标：1.结合大量现实事例，认识对称现象和轴对称图形。2.在操作、观察、画图等实际活动中，学习图形知识，发展空间观念。3.在现实生活中了解对称现象，欣赏、感受对称美，培养初步的审美素养。4.在探求知识的过程中，逐步培养学生独立思考、合作探究、自主获取知识的本领。教学重点：通过观察、操作活动，初步形成轴对称图形的空间观念。教学难点：从内心里感受到轴对称图形的特点，正确判断哪些是轴对称图形。突破措施：教师的直观演示与学生动手操作相结合，再配以大量的课外练习。课前准备：课件图片彩笔折纸小剪刀教学过程：1.教师展示几组生活中不对称的图片，让学生说一说这些图片有哪些地方不好，为引入对称作准备。2.展示教材19 页民俗节图片，让学生通过观察看能发现什么？初步了解这样的图形就是对称图形。（方法先小组讨论，汇报只靠观察得出的结论，再让学生拿出课前准备的图片折折看，再次汇报得出“图形对折后两边完全重合”的结论）精品w o r d 可编辑资料-第 1 页，共 3 页-读书破万卷下笔如有神3.在学生有了初步的感性认识后教师边演示边小结“如果一个图形对折后两边能完全重合，像这样的图形我们就叫它轴对称图形，我们折的过程中的折痕就是这个图形的对称轴。”板书：轴对称图形：对折后两边完全重合对称轴：折痕4.处理“自主练习”巩固所学知识。（1）完成自主练习第1 题学生先自己思考，然后交流自己的想法。（2）完成自主练习第2 题学生先独立思考作出判断，而后教师组织学生演示，检验刚才的判断。(3)完成自主练习第 3 题学生先判断是不是轴对称图形，再用课前准备的图形用对折的方法验证。（4）完成自主练习第4 题学生先独立完成，而后让做得快的回答自己的想法，教师小结生活中人们经常利用轴对称图形的特点来进行剪纸。课堂小结：教师提问：“这节课你有什么收获？”启发学生用自己的话总结本节所学的内容。课堂检测：1.判断下列图形，哪些是对称的？（教师出示自主练习的第1 题，让学生判断）精品w o r d 可编辑资料-第 2 页，共 3 页-文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 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题的动作，其他同学直观判断。3.剪下教材附页中的下列图形，折折看，哪些是轴对称图形？课堂小结：同学们，今天我们学习了对称，认识了许许多多的轴对称图形，你认为什么样的图形是轴对称图形呢?(学生只要能说出对折后两边重合，或者能说出轴对称图形就是物体的左右两边形状一样就行。)课外拓展：长方形有几条对称轴？正方形呢？圆呢？折一折，画一画。板书设计：对 称轴对称图形：对折后两边完全重合对称轴：折痕精品w o r d 可编辑资料-第 3 页，共 3 页-文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 ZZ4S2T6C2J4文档编码:CT6G6V9F9X7 HH1G1O1J10U9 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