八年级数学教学设计：菱形(第2课时)

这是一份八年级数学教学设计：菱形(第2课时)，共5页。教案主要包含了教学目标，教法设计，重点·难点·疑点及解决办法，课时安排，教具学具准备，师生互动活动设计，教学步骤，布置作业等内容，欢迎下载使用。
八年级数学教学设计：菱形(第2课时)　　一、教学目标1.掌握菱形的判定.2.通过运用菱形知识解决具体问题，提高分析能力和观察能力.3.通过教具的演示培养学生的学习兴趣.4.根据平行四边形与矩形、菱形的从属关系，通过画图向学生渗透集合思想.二、教法设计观察分析讨论相结合的方法三、重点·难点·疑点及解决办法1.教学重点：菱形的判定方法.2.教学难点：菱形判定方法的综合应用.四、课时安排1课时五、教具学具准备教具(做一个短边可以运动的平行四边形)、投影仪和胶片，常用画图工具六、师生互动活动设计教师演示教具、创设情境，引入新课，学生观察讨论;学生分析论证方法，教师适时点拨七、教学步骤【复习提问】1.叙述菱形的定义与性质.2.菱形两邻角的比为1：2，较长对角线为    ，则对角线交点到一边距离为________.                                                        【引入新课】师问：要判定一个四边形是不是菱形最基本的判定方法是什么方法?生答：定义法.此外还有别的两种判定方法，下面就来学习这两种方法.【讲解新课】菱形判定定理1：四边都相等的四边形是菱形.菱       形判定定理2：对角钱互相垂直的平行四边形是菱形.图1                                                                                                  分析判定1：首先证它是平行四边形，再证一组邻边相等，依定义即知为菱形.分析判定2：师问：本定理有几个条件?生答：两个.师问：哪两个?生答：(1)是平行四边形(2)两条对角线互相垂直.师问：再需要什么条件可证该平行四边形是菱形?生答：再证两邻边相等.(由学生口述证明)证明时让学生注意线段垂直平分线在这里的应用，师问：对角线互相垂直的四边形是菱形吗?为什么?可画出图，显然对角线          ，但都不是菱形.                                                                                                                                            菱形常用的判定方法归纳为(学生讨论归纳后，由教师板书)：                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       注意：(2)与(4)的题设也是从四边形出发，和矩形一样它们的题没条件都包含有平行四边形的判定条件.例4 已知：                                                                                                                                                                                                                                                                                                                                    的对角钱                                                                                                                                                                                                                                                                          的垂直平分线与边                                                                                                                                                                                                                                                                          、                                                                                                                                                                                                                                                                          分别交于                                                                                                                                                                                                                                                                          、                                                                                                                                                                                                                                                                          ，如图.                                                                                                                                                                                                                                                                          求证：四边形                                                                                                                                                                                                                                                                                                                    是菱形(按教材讲解).【总结、扩展】1.小结：(1)归纳判定菱形的四种常用方法.(2)说明矩形、                                                                                                                                                           菱形之间的区别与联系.                                                                                                                                                                                                                                                                                                                                                              2.思考题：已知：如图4△                                                                                                                                                                                                                                                                                                                                                                                                        中，                                                                                                                                                                                                                                                                                                                                                                                                        ，                                                                                                                                                                                                                                                                                                                                                                                                        平分                                                                                                                                                                                                                                                                                                                                                                                                        ，                                                                                                                                                                                                                                                                                                                                                                                                        ，                                                                                                                                                                                                                                                                                                                                                                                                        ，                                                                                                                                                                                                                                                                                                                                                                                                        交                                                                                                                                                                                                                                                                                                                                                                                                        于                                                                                                                                                                                                                                                                                                                                                                                                        .                                                                                                                                                                                                                                                                                                                                                                                                        求证：四边形                                                                                                                                                                                                                                                                                                                                                                                                                                                  为菱形.                                                                                                                                                                                                                                                                                                                                                                                                                                                  八、布置作业教材P159中9、10、11、13(2)“师”之概念，大体是从先秦时期的“师长、师傅、先生”而来。其中“师傅”更早则意指春秋时国君的老师。《说文解字》中有注曰：“师教人以道者之称也”。“师”之含义，现在泛指从事教育工作或是传授知识技术也或是某方面有特长值得学习者。“老师”的原意并非由“老”而形容“师”。“老”在旧语义中也是一种尊称，隐喻年长且学识渊博者。“老”“师”连用最初见于《史记》，有“荀卿最为老师”之说法。慢慢“老师”之说也不再有年龄的限制，老少皆可适用。只是司马迁笔下的“老师”当然不是今日意义上的“教师”，其只是“老”和“师”的复合构词，所表达的含义多指对知识渊博者的一种尊称，虽能从其身上学以“道”，但其不一定是知识的传播者。今天看来，“教师”的必要条件不光是拥有知识，更重于传播知识。九、板书设计死记硬背是一种传统的教学方式,在我国有悠久的历史。但随着素质教育的开展,死记硬背被作为一种僵化的、阻碍学生能力发展的教学方式,渐渐为人们所摒弃;而另一方面,老师们又为提高学生的语文素养煞费苦心。其实,只要应用得当,“死记硬背”与提高学生素质并不矛盾。相反,它恰是提高学生语文水平的重要前提和基础。                                                                                                                                                                                                                                                                                                                                                                                               十、随堂练习教材P153中1、2、3