2022年圆的面积教学设计说课反思2 .pdf

圆 的 面 积教学设计二 0 一六二 0 一七学年度第二学期执教：黄治国2017-5-22五年级数学下册圆的面积教学设计教学内容：国标本苏教版教科书小学数学五年级下册第9798页“圆的面积”以及相应的“练一练”、练习十五第 1 题。教学内容分析：圆的面积是学生认识了圆的特征、学会计算圆的周长以及学习过直线围成的平面图形面积计算公式的基础上进行教学的。由于以前所学图形的面积计算都是直线图形面积的计算，而像圆这样的曲边图形的面积计算，学生还是第一次接触到，所以具有一定的难度和挑战性。教学关键之处在于学生通过观察猜想、动手操作、计算验证，自主探索、推导出圆的面积公式并能灵活应用圆的面积公式解决实际问题。因此本课的教学应紧紧围绕“转化”思想，引导学生联系已学知识把新知识纳入已有知识中分析、研究、归纳，从而完成对新知的建构过程，建立数学模型，培养解决问题的综合能力。学生情况分析：小学对几何图形的认识很大程度属于直观几何的学习阶段，而几何本身比较抽象的。本节内容学生从认识直线图形发展到认识曲线图形，又是一次飞跃，但从学生思维角度看，五年级学生具有一定的抽象和逻辑思维能力。这一学段中的学生已经有了许多机会接触到数与计算、空间图形等较丰富的数学内容，已经具备了初步的归纳、类比和推理的数学活动经验，并具有了转化的数学思想。所以在教学应注意联系现实生活，组织学生利用学具开展探索性的数学活动，注重知识发现和探索过程，使学生感悟转化、极限等数学思想，从中获文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5得数学学习的积极情感，体验和感受数学的力量。同时在学习活动中，要使学生学会自主学习和小组合作，培养学生解决数学问题的能力。教学目标：1、让学生经历操作、观察、填表、验证、讨论和归纳等数学活动的过程，探索并掌握圆的面积公式，能正确计算圆的面积，并能应用公式解决相关的简单实际问题，构建数学模型。2、让学生进一步体会“转化”的数学思想方法，感悟极限思想的价值，培养运用已有知识解决新问题的能力，增强空间观念，发展数学思考。3、让学生进一步体验数学与生活的联系，感受用数学的方式解决实际问题的过程，提高学习数学的兴趣。教学重难点：重点：圆的面积计算公式的推导和应用。难点：圆的面积推导过程中，极限思想（化曲为直）的理解。教学准备：教具：多媒体课件、面积转化教具。学具：书、计算器、16 等份教具、作业纸。教学过程：一、创设情境、揭示课题1、师：大家看，一匹马被拴在木桩上，它吃草的时候绷紧绳子绕了一圈。从图中，你知道了哪些信息？（复习圆的相关特征）文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5师：那马最多能吃多大面积的草呢？师：圆所围成的平面的大小就叫做圆的面积。师：今天我们继续来研究圆的面积。（揭示课题）2、师：你想研究它的哪些问题呢？（引导学生提出疑问）【设计意图：在教学过程的伊始就用这个生活中的数学问题来导入新课的学习，既可以激起学生学习的兴趣，又可以为后面圆面积的学习奠定基础，更可以让学生从课堂上涉猎生活中的数学问题，让学生体验到数学来源于生活。】二、猜想验证、初步感知1、实验验证（1）师：猜一猜，圆的面积可能会和它的什么有关系？师：你觉得圆的面积大约是正方形的几倍？（2）师：对我们的估计需要进行？生：验证。师：用什么方法验证呢？师：下面请大家先数数圆的面积是多少。师：数起来感觉怎么样？有没有更简洁一点的方法？（引导学生发现可以先数出个圆的方格数，再乘4 就是圆的面积）（让学生在图 1 中数一数，用计算器算一算，填写表格里的第1行。）文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5（3）师：只用一个圆，还不足以验证猜想，作业纸上老师还准备了两个圆，同桌合作，分别用同样的方法把研究成果填写在表格中。（课件出示图 2 和图 3）（学生完成后交流汇报。）师：仔细观察表中的数据，你有什么发现？生：这三个圆的半径虽然不同，但是圆的面积都是它对应正方形面积的 3 倍多一些。3、师：正方形面积可以用r2表示，那圆的面积和它半径平方之间有什么关系呢？生：圆的面积是它半径平方的3 倍多一些。小结：我们经过猜测数方格验证，最终发现圆的面积是正方形面积也就是它半径平方的3 倍多一些。【设计意图：从学生熟悉的数方格开始学习圆面积的计算，有利于学生从整体上把握平面图形面积计算的学习，有利于充分激活学生已有的关于平面图形面积计算的知识和经验，从而为进一步探索圆的面积公式作好准备。由数方格获得的初步结论对接下来的转化推导相圆的半径（cm）圆的面积（2cm）正方形的面积（2cm）圆的面积大约是正方形面积的几倍（精确到十分位）文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5互印证，使学生充分感受圆面积公式推导过程的合理性。】三、实验操作、推导公式1、感受转化，渗透方法（课件再次出示马吃草图）师：知道了 3 倍多一些，就能准确算出这匹马最多可以吃多大面积的草了吗？（引导学生发现，3 倍多一些到底多多少还不清楚，需要继续研究能准确计算圆面积的方法。）2、师：大家还记得平行四边形、三角形、梯形的面积计算公式分别是如何推导出来的吗？（学生回忆后汇报，教师演示，激活转化思路）3、第一轮探究明确思路，体会转化师：想想看，圆能不能转化成学过的图形？是否可以化曲为直呢？生：剪圆。师：怎么剪呢？沿着什么剪？生：沿着直径或半径剪开。（分别演示 2 等份、4 等份、8 等份，引导学生发现边越来越直，剪拼的图形越来越接近平行四边形）4、第二轮探究明确方法，体验极限师：刚才我们将圆分别剪成4 等份、8 等份再拼成新的图形是想干什么呀？文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5生：想把圆形转化成平行四边形。师：那还能更像吗？生：可以将圆片平均分成16份。（引导学生把 16、32 等份的圆拼成近似的长方形，上台展示）师：从哪儿可以看出这两幅图更接近平行四边形了？生：边更直了。师：是什么方法使得边越来越直了？生：平均分的份数越来越多。（引导学生体验把圆平均分成64 份、128份剪拼后的图形越来越接近长方形）师：如果我们平均分的份数足够多，就化曲为直，最后拼成的图形就成长方形了。【设计意图：通过这一环节，渗透一种重要的数学思想转化，引导学生抽象概括出新的问题可以转化成旧的知识，利用旧的知识解决新的问题，从而推及到圆的面积能不能转化成以前学过的平面图形！如果能，我们可以很容易发现它的计算方法了。让学生迅速回忆，调动原有的知识，为新知识的“再创造”做好知识的准备。学生展开想象的翅膀，从而得出等分的份数愈多，拼成的图形就越接近平行四边形。在想象的过程中蕴含了另一个重要数学思想的渗透极限思想。】（2）师：我们把圆转化成了长方形，什么变了，什么没变？生：形状变了，面积大小没有变。文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5师：这样就把圆的面积转化成了？生：长方形的面积。师：要求圆的面积，只要求出？生：长方形的面积。5、第 3 轮探究深化思维，推导公式师：仔细观察剪拼成的长方形，看看它与原来的圆之间有什么联系？将发现填写在作业纸第2 题中，然后小组内交流一下。（小组讨论，发现：长方形的宽等于圆的半径，长方形的长等于圆周长的一半。）师：长方形的宽和圆的半径相等，这里的宽也可以用r 表示。那么，长方形的长又可以怎么表示呢？（重点引导学生理解长：C22r2r）（通过长方形面积计算方法，引出圆的面积计算方法）师：圆的面积是它半径平方的3 倍多一些，准确地说是它半径平方的多少倍？生：倍。师：有了这样的一个公式，知道圆的什么，就可以计算圆的面积了。生：半径。5、做“练一练”完成作业纸第 3 题，交流反馈。6、（课件再次出示牛吃草图）文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编码:CX4I2K6Z8J9 HJ9Z3X6O3X10 ZH6R9P5C7P5文档编