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推导圆的面积公式推导圆的面积公式 教学目标 1.学生通过观察、操作、分析和讨论,找出拼前圆形和拼后图形各部分之间的联系,从而推导出圆的面积公式。能够利用公式进行简单的面积计算。 2.渗透转化思想,初步了解极限思想。培养学生的观察能力和动手操作能力。 3.培养学生集体观念。利用小组合作学习,使学生养成互相合作、互相帮助的好品质。 教学重点和难点 1.学生通过自己的观察、操作,找出拼前圆的各部分与拼后图形各部分之间的联系。 2.用不同的方法推导出圆的面积公式。 教学用具 每组两个同样大的等分成16份的圆。 教学过程设计 ...

推导圆的面积公式
推导圆的面积公式 教学目标 1.学生通过观察、操作、 分析 定性数据统计分析pdf销售业绩分析模板建筑结构震害分析销售进度分析表京东商城竞争战略分析 和讨论,找出拼前圆形和拼后图形各部分之间的联系,从而推导出圆的面积公式。能够利用公式进行简单的面积计算。 2.渗透转化思想,初步了解极限思想。培养学生的观察能力和动手操作能力。 3.培养学生集体观念。利用小组合作学习,使学生养成互相合作、互相帮助的好品质。 教学重点和难点 1.学生通过自己的观察、操作,找出拼前圆的各部分与拼后图形各部分之间的联系。 2.用不同的方法推导出圆的面积公式。 教学用具 每组两个同样大的等分成16份的圆。 教学过程设计 (一)复习引课 1.投影一个圆,引出课 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 。 问:(1)你都知道圆的哪些知识, (2)已知直径怎样求圆的周长, 板 关于书的成语关于读书的排比句社区图书漂流公约怎么写关于读书的小报汉书pdf :C=πd (3)已知半径怎样求圆的周长, (4)已知半径怎样求圆周长的一半, (5)你还想学习圆的什么知识, 师:这节课我们就来满足你们的愿望。一起研究圆的面积。(投影复合出圆的面积。) 板书:圆的面积 2.质疑引趣。 师:老师家里想买一个茶叶筒。老师看上两种不同的样式(拿出实物),一个是正方形形状的,一个是圆柱体形状的。可老师家桌面很小,想买一个占桌面面积小的,我应该选哪一个 escape from debt of the bank records of actual control of enterprise and its associated spouse obtained credit support strict precautions against serious adverse credit history of borrower (guarantor) and their spouses get the Bank crediting support. Implementation of the guarantee the guarantee personal credit business, investigators should verify a guarantor willing, guarantees or credits (MS) charge status, value and evaluation of liquidity. Arrival (mass) bet property value assessments to assessment company approved by the Bank to assess reported or recognized the value of the Bank confirmation shall prevail; investigators through market price than the reciprocal verification of charge values, prevention assessed value is too high, and so on. Mortgage, status check and to verify ownership, leasing and is imposed by the existence of a relocation, and other special situations. Customer access to Customer Manager product documentation standards set by States should be in accordance with the Bank select borrowers, guarantors and bet. Section II review review-approval staff should perform their duties strictly in accordance with authorized, prohibited Super license. Approval shall, in accordance with authorized, independent approval according to their own knowledge and experience. Review 2 呢,谁能帮老师拿个主意,为什么你们都没有确切的把握,这个问题与什么知识有关,上完这节课后,看谁能帮老师解决实际问题。 3.复习旧知。 问:(1)以前我们学过哪几种平面图形的面积, (2)想一想,我们用什么方法推导出平行四边形面积公式的,(投影过程) 质疑:圆的面积公式能不能也用分割拼摆的方法把圆转化成学过的图形推导出来呢, 问:(1)圆与我们以前学过的平面图形有什么不同, (2)如何能把曲线转化成近似的线段呢,这就是我们首先要研究的问题。 (二)新授教学 问:圆的大小与谁有关, 师:沿半径把圆平均分成若干份,剪开拉直,你会发现什么, 投影:把3个等圆分别平均分成4份、8份、16份。拉开,看曲线的变化。 问:继续分,32份、64份,你发现了什么规律, 生:平均分的份数越多,曲线越趋近于直的线段。 师:这个问题解决了,我们试着把圆分割、拼摆,转化成以前学过的什么图形, 2.学生剪拼。 问:把圆平均分成若干份,沿着圆的什么分,为什么这么分, (1)每组有两个等分成16份的圆,只剪一个圆。组长先剪成4份,每人再剪,看哪组快。 师:每人拿起其中一份。圆的周长是C,这个近似三角形的底是多少, escape from debt of the bank records of actual control of enterprise and its associated spouse obtained credit support strict precautions against serious adverse credit history of borrower (guarantor) and their spouses get the Bank crediting support. Implementation of the guarantee the guarantee personal credit business, investigators should verify a guarantor willing, guarantees or credits (MS) charge status, value and evaluation of liquidity. Arrival (mass) bet property value assessments to assessment company approved by the Bank to assess reported or recognized the value of the Bank confirmation shall prevail; investigators through market price than the reciprocal verification of charge values, prevention assessed value is too high, and so on. Mortgage, status check and to verify ownership, leasing and is imposed by the existence of a relocation, and other special situations. Customer access to Customer Manager product documentation standards set by States should be in accordance with the Bank select borrowers, guarantors and bet. Section II review review-approval staff should perform their duties strictly in accordance with authorized, prohibited Super license. Approval shall, in accordance with authorized, independent approval according to their own knowledge and experience. Review (2)以小组为单位,试着拼一拼,看一看能拼成近似的什么图形。 每小组选代 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf 说一说:你们组拼成的图形近似什么图形, 生:长方形、平行四边形、梯形、三角形。 (3)把拼成的长方形放到实物投影上展示。 (4)为了看清楚长方形的拼摆全过程,看电脑演示。边看边思考下面的问题: ?拼前是什么图形,拼后近似什么图形, ?拼前图形的面积与拼后图形的面积有什么关系, ?拼后图形的长相当于圆的哪部分,宽相当于圆的哪部分, 同组互相讨论。把讨论的结果汇报一下。 3.推导公式。 根据学生的发言,老师板书: 师:我们把圆转化成了近似的长方形,根据长方形的面积公式推导出圆的面积公式: 2S,πr 我们推导的公式是否正确,下面我们用其他的方法验证一下。你们每组都拼成了不同的图形,看你们拼成的图,讨论上面4个问题。 把长换成底,把宽换成高。 同组合作,推导圆的面积公式。哪组做得又对又快,就把你们的成果展示给同学们。 (1)拼成三角形,指名说思路。 escape from debt of the bank records of actual control of enterprise and its associated spouse obtained credit support strict precautions against serious adverse credit history of borrower (guarantor) and their spouses get the Bank crediting support. Implementation of the guarantee the guarantee personal credit business, investigators should verify a guarantor willing, guarantees or credits (MS) charge status, value and evaluation of liquidity. Arrival (mass) bet property value assessments to assessment company approved by the Bank to assess reported or recognized the value of the Bank confirmation shall prevail; investigators through market price than the reciprocal verification of charge values, prevention assessed value is too high, and so on. Mortgage, status check and to verify ownership, leasing and is imposed by the existence of a relocation, and other special situations. Customer access to Customer Manager product documentation standards set by States should be in accordance with the Bank select borrowers, guarantors and bet. Section II review review-approval staff should perform their duties strictly in accordance with authorized, prohibited Super license. Approval shall, in accordance with authorized, independent approval according to their own knowledge and experience. Review 4 根据三角形面积公式可得: (2)拼成梯形,指名说思路。 根据梯形面积公式可得: (3)利用圆中的一份(近似一个三角形)也可推导出圆的面积公式。 以推导一下。 escape from debt of the bank records of actual control of enterprise and its associated spouse obtained credit support strict precautions against serious adverse credit history of borrower (guarantor) and their spouses get the Bank crediting support. Implementation of the guarantee the guarantee personal credit business, investigators should verify a guarantor willing, guarantees or credits (MS) charge status, value and evaluation of liquidity. Arrival (mass) bet property value assessments to assessment company approved by the Bank to assess reported or recognized the value of the Bank confirmation shall prevail; investigators through market price than the reciprocal verification of charge values, prevention assessed value is too high, and so on. Mortgage, status check and to verify ownership, leasing and is imposed by the existence of a relocation, and other special situations. Customer access to Customer Manager product documentation standards set by States should be in accordance with the Bank select borrowers, guarantors and bet. Section II review review-approval staff should perform their duties strictly in accordance with authorized, prohibited Super license. Approval shall, in accordance with authorized, independent approval according to their own knowledge and experience. Review 师:我们用这么多的方法推导出圆的面积公式,你们很聪明。圆的面积怎么求,求圆的面积 必须知道什么条件, 4.投影出示例3。 例3 一个圆的半径是4厘米。它的面积是多少平方厘米, (1)学生独立完成。 (2)投影订正。 (三)巩固练习 1.课前老师的问题,哪个茶叶筒的底面面积小,正方形的底面边长是8厘米,圆柱体的底面 直径是8厘米。你们算算看。 学生独立完成,投影订正。 2.一个圆的周长是6.28分米,求它的面积。 问:已知直径或周长,怎样求圆的面积, 生:必须先求出半径,再求面积。 3.思考题 (投影)已知正方形的面积是25平方厘米,求圆的面积。 讨论:(1)正方形的边长是圆的哪部分,正方形的面积怎么求, (2)圆的面积与小正方形面积r2有什么关系, 生:圆的面积是半径为边长的小正方形面积的π倍。 问:这道题怎样列式计算呢, 板书:3.14×25=78.5(平方厘米) (四)课堂总结 这节课你都学习了哪些知识,圆的面积怎么求,圆的面积与谁有关,有怎样的关系,还有 什么问题, (五)作业 课本 “做一做”1,2,题,练习的第1,2,3,4题。 课堂教学设计 说明 关于失联党员情况说明岗位说明总经理岗位说明书会计岗位说明书行政主管岗位说明书 escape from debt of the bank records of actual control of enterprise and its associated spouse obtained credit support strict precautions against serious adverse credit history of borrower (guarantor) and their spouses get the Bank crediting support. Implementation of the guarantee the guarantee personal credit business, investigators should verify a guarantor willing, guarantees or credits (MS) charge status, value and evaluation of liquidity. Arrival (mass) bet property value assessments to assessment company approved by the Bank to assess reported or recognized the value of the Bank confirmation shall prevail; investigators through market price than the reciprocal verification of charge values, prevention assessed value is too high, and so on. Mortgage, status check and to verify ownership, leasing and is imposed by the existence of a relocation, and other special situations. Customer access to Customer Manager product documentation standards set by States should be in accordance with the Bank select borrowers, guarantors and bet. Section II review review-approval staff should perform their duties strictly in accordance with authorized, prohibited Super license. Approval shall, in accordance with authorized, independent approval according to their own knowledge and experience. Review 6 1.本节课采用了分小组合作学习的方法,效果较好。第一,分小组学习,学生们互相配合节省时间,提高课堂效率。如:把圆剪成16等份,如果一个人完成很困难,但4人合作就很快了。再如:推导圆的面积公式时,学生们开动脑筋,每组都用不同的方法推导出面积公式。然后通过讲思路扩大学生的信息量,使每个学生都能在有限的时间内了解多种不同的推导方法。第二,充分发挥学生的主体作用。每个学生真正成为课堂的主人,他们有时间、有机会发表自己的看法,听取别人的意见,学生们互相交流,取长补短,达到共识。 2.利用多种电教手段辅助教学。这样既可画龙点睛,激发兴趣,又大大提高了课堂效率,特别是实物投影,省时、省力,事半功倍。 板书设计 escape from debt of the bank records of actual control of enterprise and its associated spouse obtained credit support strict precautions against serious adverse credit history of borrower (guarantor) and their spouses get the Bank crediting support. Implementation of the guarantee the guarantee personal credit business, investigators should verify a guarantor willing, guarantees or credits (MS) charge status, value and evaluation of liquidity. Arrival (mass) bet property value assessments to assessment company approved by the Bank to assess reported or recognized the value of the Bank confirmation shall prevail; investigators through market price than the reciprocal verification of charge values, prevention assessed value is too high, and so on. Mortgage, status check and to verify ownership, leasing and is imposed by the existence of a relocation, and other special situations. Customer access to Customer Manager product documentation standards set by States should be in accordance with the Bank select borrowers, guarantors and bet. Section II review review-approval staff should perform their duties strictly in accordance with authorized, prohibited Super license. Approval shall, in accordance with authorized, independent approval according to their own knowledge and experience. Review
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