与三角形有关的线段

与三角形有关的线段 龙文教育教师1对1个性化 学生教师 授课 授课 2013.8.21 16:00,18:00 章心怡 罗华谍 姓名 姓名 日期 时段 课题 三角形的线段与角 1、了解学生知识掌握和学习习惯 教学2、促进知识掌握和学习习惯养成 3、学生思维和学习的提高 目标 教学过程: 教 一、教学衔接,课前环节, 学 步 1、回收上次课的教案～了解家长的反馈意见, 骤 及 2、检查学生的作业～及时指点 教 学 二、教学内容 内 容 1、三角形有关线段 知识点2、三角形相关的角 三、教学辅助练习 练习1、三角形线段练习 练习2、三角形中的角练习 四、知识 五、知识的延伸和拓展 六、布置作业 教导处签字: 日期: 年 月 日 and other bad habits. Implementation to grab at the front, the maximum possible for jobs initiative to achieve efficient service. To carry forward the meticulous, detailed style. In the Office is no small matter. Business services a small mistake, it is possible to order at its meetings disrupted the entire, feedback on the content and timing a bit negligent, it could work in a passive position, slightly poor reception, may affect the image of a place and unit. Therefore, the Office staff with a high degree of professionalism and responsibility, serious and responsible, meticulous, careful to do everything to ensure that globalSmoothly. To carry forward the hard work, honest style. Adhere to the "Ning public and poverty, is not private and rich" old adage, bearing in mind the purpose of serving, consciously resist the erosion of various corruption and self-discipline, integrity, do not take leadership on behalf of the Office for personal affairs, not banner of leading organs of self-serving, and always maintain and carry forward the fine style of hard work, thrift and career, be honest and upright. Comrades, Government Office work task is glorious, a great responsibility. Hope the city's system of Government Office around the overall situation, pay attention to implementation of work in the purpose, give full play to staff aides, integrated and coordinated implementation, supervision, service functions, close contact, strengthen coordination, collaboration, efforts for grass-roots leadership services, service, quality and level of services for the masses to push to a new level. 2003 annual summary meeting of the Office of the municipal government reports on innovation 教学过 程中学 生易错 点归类 作业布 置 一、 学生对于本次课的评价 O 特别满意 O 满意 O 一般 O 差 学习过二、 教师评定 程评价 1、 学生上次作业评价 O好 O较好 O 一般 O差 2、 学生本次上课情况评价 O 好 O 较好 O 一般 O 差 家长 意见 家长签名: and other bad habits. Implementation to grab at the front, the maximum possible for jobs initiative to achieve efficient service. To carry forward the meticulous, detailed style. In the Office is no small matter. Business services a small mistake, it is possible to order at its meetings disrupted the entire, feedback on the content and timing a bit negligent, it could work in a passive position, slightly poor reception, may affect the image of a place and unit. Therefore, the Office staff with a high degree of professionalism and responsibility, serious and responsible, meticulous, careful to do everything to ensure that globalSmoothly. To carry forward the hard work, honest style. Adhere to the "Ning public and poverty, is not private and rich" old adage, bearing in mind the purpose of serving, consciously resist the erosion of various corruption and self-discipline, integrity, do not take leadership on behalf of the Office for personal affairs, not banner of leading organs of self-serving, and always maintain and carry forward the fine style of hard work, thrift and career, be honest and upright. Comrades, Government Office work task is glorious, a great responsibility. Hope the city's system of Government Office around the overall situation, pay attention to implementation of work in the purpose, give full play to staff aides, integrated and coordinated implementation, supervision, service functions, close contact, strengthen coordination, collaboration, efforts for grass-roots leadership services, service, quality and level of services for the masses to push to a new level. 2003 annual summary meeting of the Office of the municipal government reports on innovation 7.1 与三角形有关的线段 7.1.1 三角形的边 考点1:认识三角形 1.如图7.1.1-1的三角形记作__________，它的三条边是__________，三个顶点分别是_________，三个内角是__________， 顶点A、B、C所对的边分别是___________，用小写字母分别示为 __________. 图7.1.1-1 图7.1.1-2 2.三角形按边分类可分为__________三角形，__________三角形;等腰三角形分为底与腰__________ 的三角形和底与腰__________的三角形. 3.如图7.1.1-2所示，以AB为一边的三角形有( ) A.3个 B.4个 C.5个 D.6个 考点2:三角形三边关系 4.已知四组线段的长分别如下，以各组线段为边，能组成三角形的是( ) A.1，2，3 B.2，5，8 C.3，4，5 D.4，5，10 5.(2008?福州)已知三角形的两边长分别为4cm和9cm，则下列长度的四条线段中能作为第三边的是( ) A.13cm B.6cm C.5cm D.4cm 6.如果线段a、b、c能组成三角形，那么，它们的长度比可能是( ) A.1?2?4 B.1?3?4 C.3?4?7 D.2?3?4 7.已知等腰三角形的两边长分别为4cm和7cm，则此三角形的周长为( ) A.15cm B.18cm C.15cm或18cm D.不能确定 8.下列各组给出的三条线段中不能组成三角形的是( ) A.3，4，5 B.3a，4a，5a C.3+a，4+a，5+a D.三条线段之比为3?5?8 9.三角形三边的比是3?4?5，周长是96cm，那么三边分别是________cm. 10.已知等腰三角形的周长是25cm，其中一边长为10cm，求另两边长__________. 11.某木材市场上木棒规格和价格如下表: 规格 1m 2m 3m 4m 5m 6m 价格(元/根) 10 15 20 25 30 35 小明的爷爷要做一个三角形的木架养鱼用，现有两根长度为3m和5m的木棒，还需要到某木材市 场上购买一根.问:(1)有几种规格的木棒可供小明的爷爷选择,(2)选择哪一种规格的木棒最 省钱, l government reports on innovationuality and level of services for the masses to push to a new level. 2003 annual summary meeting of the Office of the municiparoots leadership services, service, q-service functions, close contact, strengthen coordination, collaboration, efforts for grass implementation of work in the purpose, give full play to staff aides, integrated and coordinated implementation, supervision, Hope the city's system of Government Office around the overall situation, pay attention to- is glorious, a great responsibility. nd carry forward the fine style of hard work, thrift and career, be honest and upright. Comrades, Government Office work taskserving, and always maintain a-elfdiscipline, integrity, do not take leadership on behalf of the Office for personal affairs, not banner of leading organs of sng in mind the purpose of serving, consciously resist the erosion of various corruption and selfAdhere to the "Ning public and poverty, is not private and rich" old adage, beari To carry forward the hard work, honest style. fessionalism and responsibility, serious and responsible, meticulous, careful to do everything to ensure that globalSmoothly.f proposition, slightly poor reception, may affect the image of a place and unit. Therefore, the Office staff with a high degree o to order at its meetings disrupted the entire, feedback on the content and timing a bit negligent, it could work in a passivethe meticulous, detailed style. In the Office is no small matter. Business services a small mistake, it is possible Implementation to grab at the front, the maximum possible for jobs initiative to achieve efficient service. To carry forward bad habits. and other 3 7.1.2 三角形的高、中线与角平分线 考点1:三角形的高 1.如图7.1.2-1，在?ABC中，BC边上的高是________;在?AFC中，CF边上的高是________;在?ABE中，AB边上的高是_________. 图7.1.2-1 图7.1.2-2 图7.1.2-3 2.如图7.1.2-2，?ABC的三条高AD、BE、CF相交于点H，则?ABH的三条高是_______，这三条高交于________.BD是?________、?________、?________的高. 3.如图7.1.2-3，在?ABC中EF?AC，BD?AC于D，交EF于G，则下面说话中错误的是( ) A.BD是?ABC的高 B.CD是?BCD的高 C.EG是?ABD的高 D.BG是?BEF的高 4.如果一个三角形的三条高的交点恰是三角形的一个顶点，那么这个三角形是( ) A.锐角三角形 B.直角三角形 C.钝角三角形 D.不能确定 5.三角形的三条高的交点一定在( ) A.三角形内部 B.三角形的外部 C.三角形的内部或外部 D.以上都不对 6.如图7.1.2-4所示，?ABC中，边BC上的高画得对吗,为什么, 图7.1.2-4 :三角形的中线与角平分线 考点2 7如图7.1.2-5所示:(1)AD?BC，垂足为D，则AD是________的高，?________= ?________=90?. 1(2)AE平分?BAC，交BC于E点，则AE叫做?ABC的________，?________=?________=?2 ________. (3)若AF=FC，则?ABC的中线是________，S=________. ?ABF (4)若BG=GH=HF，则AG是________的中线，AH是________的中线. 图7.1.2-5 图7.1.2-6 8.如图7.1.2-6，DE?BC，CD是?ACB的平分线，?ACB=60?，那么?EDC=______度. 19.如图7.1.2-7，BD=DC，?ABN=?ABC，则AD是?ABC的________线，BN是?ABC的________，ND2 是?BNC的________线. and other bad habits. Implementation to grab at the front, the maximum possible for jobs initiative to achieve efficient service. To carry forward the meticulous, detailed style. In the Office is no small matter. Business services a small mistake, it is possible to order at its meetings disrupted the entire, feedback on the content and timing a bit negligent, it could work in a passive position, slightly poor reception, may affect the image of a place and unit. Therefore, the Office staff with a high degree of professionalism and responsibility, serious and responsible, meticulous, careful to do everything to ensure that globalSmoothly. To carry forward the hard work, honest style. Adhere to the "Ning public and poverty, is not private and rich" old adage, bearing in mind the purpose of serving, consciously resist the erosion of various corruption and self-discipline, integrity, do not take leadership on behalf of the Office for personal affairs, not banner of leading organs of self-serving, and always maintain and carry forward the fine style of hard work, thrift and career, be honest and upright. Comrades, Government Office work task is glorious, a great responsibility. Hope the city's system of Government Office around the overall situation, pay attention to implementation of work in the purpose, give full play to staff aides, integrated and coordinated implementation, supervision, service functions, close contact, strengthen coordination, collaboration, efforts for grass-roots leadership services, service, quality and level of services for the masses to push to a new level. 2003 annual summary meeting of the Office of the municipal government reports on innovation 图7.1.2-7 图7.1.2-8 10.如图7.1.2-8，若上?1=?2、?3=?4，下列结论中错误的是( ) A.AD是?ABC的角平分线 B.CE是?ACD的角平分线 1C.?3=?ACB D.CE是?ABC的角平分线 2 11.下列判断中，正确的个数为( ) (1)D是?ABC中BC边上的一个点，且BD=CD，则AD是?ABC的中线 (2)D是?ABC中BC边上的一个点，且?ADC=90?，则AD是?ABC的高 1(3)D是?ABC中BC边上的一个点，且?BAD=?BAC，则AD是?ABC的角平分线 2 (4)三角形的中线、高、角平分线都是线段 A.1 B.2 C.3 D.4 212.如图图7.1.2-9所示，在?中，、分别是、的中点，=4cm，求. ABCDEBCADSS?ABC?ABE 图7.1.2-9 13.根据你画图的实践，用序号字母填写下表(有几种可能情况填写几个字母): A.在三角形的内部 B.在三角形的边上 C.在三角形的外部 锐角三角形 直角三角形 钝角三角形 角平分线 中线 高 7.1.3 三角形的稳定性 考点1:三角形的稳定性 1.三角形是具有________的图形，而四边形没有________. 2.自行车用脚架撑放比较稳定的原因是________. 3.木工师傅在做完门框后，为了防止变形常常像图7.1.3-1所示那样钉上两条斜拉的木板条(即图中的AB、CD两个木条)，这样做根据数学道理是____________. 图7.1.3-1 图7.1.3-2 l government reports on innovationimplementation of work in the purpose, give full play to staff aides, integrated and coordinated implementation, supervision,uality and level of services for the masses to push to a new level. 2003 annual summary meeting of the Office of the municiparoots leadership services, service, q-service functions, close contact, strengthen coordination, collaboration, efforts for grass Hope the city's system of Government Office around the overall situation, pay attention to is glorious, a great responsibility. nd carry forward the fine style of hard work, thrift and career, be honest and upright. Comrades, Government Office work taskserving, and always maintain a-elfdiscipline, integrity, do not take leadership on behalf of the Office for personal affairs, not banner of leading organs of s-ng in mind the purpose of serving, consciously resist the erosion of various corruption and selfAdhere to the "Ning public and poverty, is not private and rich" old adage, beari To carry forward the hard work, honest style. fessionalism and responsibility, serious and responsible, meticulous, careful to do everything to ensure that globalSmoothly.f proposition, slightly poor reception, may affect the image of a place and unit. Therefore, the Office staff with a high degree o to order at its meetings disrupted the entire, feedback on the content and timing a bit negligent, it could work in a passivethe meticulous, detailed style. In the Office is no small matter. Business services a small mistake, it is possible Implementation to grab at the front, the maximum possible for jobs initiative to achieve efficient service. To carry forward bad habits. and other 5 考点2:四边形的不稳定性 4.如图7.1.3-2是放缩尺，其工作原理是______________. 5下列把四边形的不稳定性合理地应用到生产实际中的例子有( ) (1)活动挂架 (2)放缩尺 (3)屋顶钢架 (4)能够推拢和拉开的铁拉门 (5)自行车的车架 (6)大桥钢架 A.1 B.2 C.3 D.4 6.下列图形(如图7.1.3-3)中哪些具有稳定性, 图7.1.3-3 7.如图7.1.3-4，哪些应用了三角形的稳定性，些应用了四边形的不稳定性. 钢架桥 起重机 屋顶钢架 活动滑门 图7.1.3-4 7.1 三角形有关的线段 7.1.1 三角形的边 1.?ABC，AB、BC、CA，A、B、C，?A、?B、?C，BC、AC、AB，a、b、c 2.不等边 等腰 不相等 相等 3.B 4.C 5.B 6.D 7.C 8.D 9.24，32，40 10.10cm，5cm或7.5cm，7.5cm 11((1)4种 (2)3m 7.1.2 三角形的高、中线与角平分线 1.AD，AF，BE 2.AE，BD，FH，C，ABH，BHD，ABD 3.C 4.B 5.D 6.(1)(2)(4)不对，(3)对，理由:图(1)、(2)、(4)中没有从A点向BC引垂线段.图(3)中符合三角形高的概念. 提示:三角形的高实际上是这条边所对的顶点到这条边的一条垂线段，若这条垂线与对边不相交，则把这条边延长，如图(3)即是一例. 7((1)BC边，ADB，ADC (2)角平分线，BAE，CAE，BAC (3)BF，S ?CBF (4)?ABH的边BH上，?AGF的边GF上 8.30 9.BC边上的中，角平分线，BC边上的中 10.D 11.D 212. S=1 cm 13.A、A、A; A、A、A;A、AB、AC ?ABE 7.1.3 三角形的稳定性 1.稳定性;稳定性 2.三角形具有稳定性 3.三角形具有稳定性 4.四边形的不稳定性 5.C 6.(1)(3)均是由三角形组成所以组合图形具有稳定性;(2)由三角形和四边形组合而成的图形不具有稳定性 7. 应用了三角形稳定性的有:钢架桥、起重机、屋顶钢架.应用了四边形不稳定性的有:活动滑门. and other bad habits. Implementation to grab at the front, the maximum possible for jobs initiative to achieve efficient service. To carry forward the meticulous, detailed style. In the Office is no small matter. Business services a small mistake, it is possible to order at its meetings disrupted the entire, feedback on the content and timing a bit negligent, it could work in a passive position, slightly poor reception, may affect the image of a place and unit. Therefore, the Office staff with a high degree of professionalism and responsibility, serious and responsible, meticulous, careful to do everything to ensure that globalSmoothly. To carry forward the hard work, honest style. Adhere to the "Ning public and poverty, is not private and rich" old adage, bearing in mind the purpose of serving, consciously resist the erosion of various corruption and self-discipline, integrity, do not take leadership on behalf of the Office for personal affairs, not banner of leading organs of self-serving, and always maintain and carry forward the fine style of hard work, thrift and career, be honest and upright. Comrades, Government Office work task is glorious, a great responsibility. Hope the city's system of Government Office around the overall situation, pay attention to implementation of work in the purpose, give full play to staff aides, integrated and coordinated implementation, supervision, service functions, close contact, strengthen coordination, collaboration, efforts for grass-roots leadership services, service, quality and level of services for the masses to push to a new level. 2003 annual summary meeting of the Office of the municipal government reports on innovation 一、选择题: 1.已知三条线段的比是:?1:3:4;?1:2:3;?1:4:6;?3:3:6;?6:6:10;?3:4:5.其中可构成三角形的有( ) A.1个 B.2个 C.3个 C.4个 2.如果三角形的两边长分别为3和5,则周长L的取值范围是( ) A.6(AB+BC+AC). 2 A P BC2.已知等腰三角形的两边长分别为4,9,求它的周长. 3.如图，分别画出每个三角形过顶点A的中线、角平分线和高。 A A A C C B C B B (2) (3) (1) and other bad habits. Implementation to grab at the front, the maximum possible for jobs initiative to achieve efficient service. To carry forward the meticulous, detailed style. In the Office is no small matter. Business services a small mistake, it is possible to order at its meetings disrupted the entire, feedback on the content and timing a bit negligent, it could work in a passive position, slightly poor reception, may affect the image of a place and unit. Therefore, the Office staff with a high degree of professionalism and responsibility, serious and responsible, meticulous, careful to do everything to ensure that globalSmoothly. To carry forward the hard work, honest style. Adhere to the "Ning public and poverty, is not private and rich" old adage, bearing in mind the purpose of serving, consciously resist the erosion of various corruption and self-discipline, integrity, do not take leadership on behalf of the Office for personal affairs, not banner of leading organs of self-serving, and always maintain and carry forward the fine style of hard work, thrift and career, be honest and upright. Comrades, Government Office work task is glorious, a great responsibility. Hope the city's system of Government Office around the overall situation, pay attention to implementation of work in the purpose, give full play to staff aides, integrated and coordinated implementation, supervision, service functions, close contact, strengthen coordination, collaboration, efforts for grass-roots leadership services, service, quality and level of services for the masses to push to a new level. 2003 annual summary meeting of the Office of the municipal government reports on innovation