2022年人教版小学数学四年级下册第五单元三角形的内角和 .pdf

Learn General Secretary on two to learn a strengthe ning four Consciousnesse s important speech cause d a strong reaction in the country. ime, watching red treasure, the origin of building the party back to power, how to strengthen services for the masses, improve party cohesion, fighting to become the grass-roots party members and masses hot topic. Grass-roots party organizations two is to strengthen the service of party members and cadre s, the pione er spirit. Distribution of grass-roots party organizations in all walks of pe ople, clothing, shelter, which bel ongs to the ne rve endings of the party organization and comments reputation has a direct perce ption of the masses. Strengthen the party ahead of the pedal spirit; strengthen the party members and cadre s success does not have to be me and t he first to bear hardships, the last to service spirit to set the partys positive image among the peopl e is important. Grass-roots party organizations two is to cle anse all people not happy not to seestereotypes, establish the honest faithful, diligent faith for the pe opl e. No need to avoid mentioning that, some members of our party can not sta nd the money, corrosion of temptation, thin, Xu Zhou, such abuse and corrupt bribery, malfeasance borers, and rats. Two, is to clean up, thin, Xu, Zhous solution to restore the partys fresh and natural, soli d and honest work style. Cleansing take, eat, card, undesirable and behaviour, cross, hard and cold, push attitude. Grass-roots party organizations two is to strengthen the sense of ordinary party members, participating i n consciousness, unity consciousness. F or reasons known, members of grass-roots party branches less mobile, less resources, and the construction of party organizations have some lag. Two studies, is to focus on the grass-roots party branches loose, soft, loose probl em, advance the party members and cadres, a gang working, Hong Kong report. Strong cleanup actions, style and rambling, presumptuous unqualified party members, pays spe cial attention to party members and cadres joining party of thought problem. Party building is obtained in the long-term development of our partys historical experience accumulated. Two is our party under the new historical conditi ons, strengthen the partys construction of a new rectification movement. Grass-roots party organizations should always catch the hard work, results-ori ented. Two educational outcomes are long-term oriented and become a n important impetus for the work. Two should have three kinds of consciousness two study and education, basic lear ning lies in the doi ng. Only the Constitution address the series of party rules, and do soli d work, be qualified party members had a soli d ide ologi cal basis. Only the learning and do real unity, to form a learn-learn-do-do the virtuous cycle , and ultimately achieve the fundamental objective of education. This requires that the Organizationlearning education, need three kinds of consciousness: one is to establish an integrated awareness. Learning and do what car isTwo-wheel, bird wi ngs, need to go hand in hand, one end can be negl ected. Communist theoretician and man. Only by closely combining theory and practi ce together in order to truly realize their value. Learning is the Foundation, the Foundation is not strong, shaking; Is the key to net to net thousands of accounts. Two education, lay the basis, going to do the key grip, so that the learning and doing back to standard, so that the majority of party members learn learning theory of nutrients, in the doing practice partys purposes. Second, to establish a sense of depth. Learning and do not Chu drawn, entirely different, but the organic unity of the whol e. Two learning education, we need to explore integrating learning in do, exhibit do in Science. To avoid the learning into simple room instruction, do int o a monotone for doing. Should exploration learn in the has do, do in the has learn of education and practice of carrier, makes general grass-roots members can in learn in the has do of achievements sense, in do in t he has learn of get sense, real makes party of theory brain into heart, put for people service concept outside of Yu shaped. Third, to adhere to long-term the awareness. Style construction on the road forever, two had to catch the long-term. Two study and education, by no means, a ssa ult-style wind-sport, but the recurrent education within the party. In recent years, the partys mass line education practice nd three-three special education i n grass-root s borne rich fruits, vast numbers of party members and cadres withstood the baptism of the spirit. Two greater need to focus on longer hold long-term, to establish and perfect the effective mecha nism of the education, focusing on the creation of long-term education, strive to make the vast number of party members to maintain their vanguard Color, maintain the partys advanced nature and purity. Awareness-raising, antennas and atmosphere a discussion on how l eading cadres of party members two current, two activity is in full swing up and down the country, party cadres as a key minority is both a barometer and impetus. The two meaning enough deep, is to determine the par ty cadres can resolve to study hard first. In the two in the pr ocess, some cadres of himself, standing long, high awareness, that Constitution Party rules is simple, its not worth bothering some party cadres think speak series has nothi ng to do with the grass-roots work, water business learning series of speeches see n as wi ndow dressing. These lazy, casual, and decade nt ideas learning la cks motivation, a serious impediment to two effect. John Stuart Mill once said, only a basic element of human thought patterns change dramatically, human destiny ca n make great improvement. The same, only party members and第四课时：三角形内角和教学内容义务教育课程标准试验教科书数学(人教版 ) 四年级下册第 85页。教学目标1. 让学生亲自动手，通过量、剪、拼等活动发现、证实三角形内角和是180，并会应用这一知识解决生活中简单的实际问题。2. 让学生在动手获取知识的过程中，培养学生的创新意识、探索精神和实践能力。并通过动手操作把三角形内角和转化为平角的探究活动，向学生渗透“ 转化” 数学思想。3. 使学生体验成功的喜悦，激发学生主动学习数学的兴趣。教学重点让学生经历 “ 三角形内角和是 180” 这一知识的形成、发展和应用的全过程。教学准备多媒体课件、学具。教学过程一、激趣引入（一）认识三角形内角师：我们已经认识了什么是三角形，谁能说出三角形有什么特点？生1：三角形是由三条线段围成的图形。生2：三角形有三个角，师：请看屏幕 ( 课件演示三条线段围成三角形的过程)。师：三条线段围成三角形后，在三角形内形成了三个角，（课件分别闪烁三个角及的弧线），我们把三角形里面的这三个角分别叫做三角形的内角。 设计意图： 通过学生回顾已学知识对三角形有一个更为深刻的认识，特别是让学生认识什么是内角非常有必要，是对学生概念认识的培养。 （二）设疑，激发学生探究新知的心理师：请同学们任意画一个三角形，能做到吗？生：能。师：请听要求，画一个有两个内角是直角的三角形，开始。（设置矛盾，使学生在矛盾中去发现问题、探究问题。）师：有谁画出来啦？生1：不能画。生2：只能画两个直角。生3：只能画长方形。师（课件演示）：是不是画成这个样子了？哦，只能画两个直角。师：问题出现在哪儿呢？这一定有什么奥秘？想不想知道？生：想。师：那就让我们一起来研究吧！（揭示矛盾，巧妙引入新知的探究） 设计意图： 借助矛盾让学生明确三角形内角和的取值范围，为下面进一步研究打精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 1 页，共 5 页Learn General Secretary on two to learn a strengthe ning four Consciousnesse s important speech cause d a strong reaction in the country. ime, watching red treasure, the origin of building the party back to power, how to strengthen services for the masses, improve party cohesion, fighting to become the grass-roots party members and masses hot topic. Grass-roots party organizations two is to strengthen the service of party members and cadre s, the pione er spirit. Distribution of grass-roots party organizations in all walks of pe ople, clothing, shelter, which bel ongs to the ne rve endings of the party organization and comments reputation has a direct perce ption of the masses. Strengthen the party ahead of the pedal spirit; strengthen the party members and cadre s success does not have to be me and t he first to bear hardships, the last to service spirit to set the partys positive image among the peopl e is important. Grass-roots party organizations two is to cle anse all people not happy not to seestereotypes, establish the honest faithful, diligent faith for the pe opl e. No need to avoid mentioning that, some members of our party can not sta nd the money, corrosion of temptation, thin, Xu Zhou, such abuse and corrupt bribery, malfeasance borers, and rats. Two, is to clean up, thin, Xu, Zhous solution to restore the partys fresh and natural, soli d and honest work style. Cleansing take, eat, card, undesirable and behaviour, cross, hard and cold, push attitude. Grass-roots party organizations two is to strengthen the sense of ordinary party members, participating i n consciousness, unity consciousness. F or reasons known, members of grass-roots party branches less mobile, less resources, and the construction of party organizations have some lag. Two studies, is o focus on the grass-roots party branches loose, soft, loose probl em, advance the party members and cadres, a gang working, Hong Kong report. Strong cleanup actions, style and rambling, presumptuous unqualified party members, pays spe cial attention to party members and cadres joining party of thought problem. Party building is obtained in the long-term development of our partys historical experience accumulated. Two is our party under the new historical conditi ons, strengthen the partys construction of a new rectification movement. Grass-roots party organizations should always catch the hard work, results-ori ented. Two educational outcomes are long-term oriented and become a n important impetus for the work. Two should have three kinds of consciousness two study and education, basic lear ning lies in the doi ng. Only the Constitution address the series of party rules, and do soli d work, be qualified party members had a soli d ide ologi cal basis. Only the learning and do real unity, to form a learn-learn-do-do the virtuous cycle , and ultimately achieve the fundame ntal objective of education. This requires that the Organizationearning education, nee d three kinds of consciousness: one i s to establish an integrated awareness. Learning a nd do what car isTwo -wheel, bir d wings, need to go hand in hand, one end can be negle cted. Communist theoretician and man. Only by closely combining theory and practice together in order to truly realize their value. Learning is the Foundation, the Foundation is not strong, shaking; Is the key to net to net thousands of accounts. Two education, lay the basis, going to do the key grip, so that the learning and doing back to standard, so that the majority of party members learn learning theory of nutrients, in the doing practice partys purposes. Second, to establish a sense of depth. Learning and do not Chu drawn, entirely different, but the organic unity of the whole. Two learning education, we need to explore integrating learning in do, exhibit do in Science. To avoid the learning into simple room instruction, do int o a monotone for doing. Should exploration learn in the has do, do in the has learn of education and practice of carrier, makes general grass-roots members can in learn in the has do of achievements sense, in do in t he has learn of get sense, real makes party of theory brain into heart, put for people service concept outside of Yu shaped. Third, to adhere to long-term the awareness. Style construction on the road forever, two had to catch the long-term. Two study and education, by no means, a ssa ult-style wind-sport, but the recurrent education within the party. In recent years, the partys mass line education practice nd three-three special education i n grass-root s borne rich fruits, vast numbers of party members and cadres withstood the baptism of the spirit. Two greater need to focus on longer hold long-term, to establish and perfect the effective mecha nism of the education, focusing on the creation of long-term education, strive to make the vast number of party members to maintain their vanguard Color, maintain the partys advanced nature and purity. Awareness-raising, antennas and atmosphere a discussion on how l eading cadres of party members two current, two activity is in full swing up and down the country, party cadres as a key minority is both a barometer and impetus. The two meaning enough deep, is to determine the par ty cadres can resolve to study hard first. In the two in the pr ocess, some cadres of himself, standing long, high awareness, that Constitution Party rules is simple, its not worth bothering some party cadres think speak series has nothi ng to do with the grass-roots work, water business learning series of speeches see n as wi ndow dressing. These lazy, casual, and decade nt ideas learning la cks motivation, a serious impediment to two effect. John Stuart Mill once said, only a basic element of human thought patterns change dramatically, human destiny ca n make great improvement. The same, only party members and下基础。 二、动手操作，探究新知（一）研究特殊三角形的内角和师：请看屏幕。（播放课件） 熟悉这副三角板吗？请拿出形状与这块一样的三角板，并同桌互相指一指各个角的度数。（课件闪动其中的一块三角板）生：90、60、30。（课件演示：由三角板抽象出三角形）师：也就是这个三角形各角的度数。它们的和怎样？生：是 180。师：你是怎样知道的？生：90+60+30=180。师：对，把三角形三个内角的度数合起来就叫三角形的内角和。师：（课件演示另一块三角板的各角的度数。）这个呢？它的内角和是多少度呢？生：90+45+45=180。师：从刚才两个三角形内角和的计算中，你发现什么？生1：这两个三角形的内角和都是180。生2：这两个三角形都是直角三角形，并且是特殊的三角形。 设计意图： 让学生经历从特殊到一般的研究过程，使学生明白要想得到一个结论指通过特例是不行的，可以先借助特例研究出的结果，然后研究一般例子来验证是否是一样的结论。经历过程比得到一个结论更重要。 （二）研究一般三角形内角和1. 猜一猜。师：猜一猜其它三角形的内角和是多少度呢？同桌互相说说自己的看法。生1：180。生2：不一定。2. 操作、验证一般三角形内角和是180。（1）小组合作、进行探究。师： 所有三角形的内角和究竟是不是180， 你能用什么办法来证明， 使别人相信呢？生：可以先量出每个内角的度数，再加起来。师：哦，也就是测量计算，是吗？那就请四人小组共同研究吧！师：每个小组都有不同类型的三角形。每种类型的三角形都需要验证，先讨论一下，怎样才能很快完成这个任务。（课前每个小组都发有锐角三角形、直角三角形、钝角三角形，指导学生选择解决问题的策略，进行合理分工，提高效率。）（2）小组汇报结果。师：请各小组汇报探究结果。生1：180。生2：175。生3：182。 设计意图： 让学生明白在研究的过程中会出现误差，但出现误差时我们应该做的是另寻方法得到结论。 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 2 页，共 5 页（三）继续探究师：没有得到统一的结果。这个办法不能使人很信服，怎么办？还有其它办法吗？生1：有。生2：用拼合的办法，就是把三角形的三个内角放在一起，可以拼成一个平角。师：怎样才能把三个内角放在一起呢？生：把它们剪下来放在一起。1. 用拼合的方法验证。师：很好，请用不同的三角形来验证。师：小组内完成，仍然先分工怎样才能很快完成任务，开始吧。2. 汇报验证结果。师：先验证锐角三角形，我们得出什么结论？生1：锐角三角形的内角拼在一起是一个平角，所以锐角三角形的内角和是180。生2：直角三角形的内角和也是180。生3：钝角三角形的内角和还是180。3. 课件演示验证结果。师：请看屏幕，老师也来验证一下，是不是跟你们得到的结果一样？（播放课件）师：我们可以得出一个怎样的结论？生：三角形的内角和是 180。（教师板书：三角形的内角和是180学生齐读一遍。）师：为什么用测量计算的方法不能得到统一的结果呢？生1：量的不准。生2：有的量角器有误差。师：对，这就是测量的误差。师：现在谁能说说不能画出有两个直角的一个三角形的原因？（让学生体验成功的喜悦）生：因为三角形的内角和是 180，在一个三角形中如果有两个直角，它的内角和就大于180。师：在一个三角形中，有没有可能有两个钝角呢？生：不可能。师：为什么？生：因为两个锐角和已经超过了180。师：那有没有可能有两个锐角呢？生：有，在一个三角形中最少有两个内角是锐角。 设计意图： 锻炼学生的思维创新意识，让学生在小组讨论合作交流的过程中得出三角形内角和的结论，经历思考、验证的过程。 三、知识应用1. 看图求出未知角的度数。（知识的直接运用，数学信息很浅显）2. 按要求计算。（数学信息较为隐藏和生活中的实际问题）3. 游戏巩固。在四人小组中完成：由一个同学出题，其它三个同学回答。（1）给出三角形两个内角， 说出另外一个内角 （有唯一的答案） 。 （2）给出三角形一个内角，说出其它两个内角（答案不唯一，可以得出无数个答案）。精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 3 页，共 5 页Learn General Secretary on two to learn a strengthe ning four Consciousnesse s important speech cause d a strong reaction in the country. ime, watching red treasure, the origin of building the party back to power, how to strengthen services for the masses, improve party cohesion, fighting to become the grass-roots party members and masses hot topic. Grass-roots party organizations two is to strengthen the service of party members and cadre s, the pione er spirit. Distribution of grass-roots party organizations in all walks of pe ople, clothing, shelter, which bel ongs to the ne rve endings of the party organization and comments reputation has a direct perce ption of the masses. Strength