角的比较与运算(公开课)课件

单击此处编辑母版标题样式,单击此处编辑母版文本样式,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,单击此处编辑母版标题样式,单击此处编辑母版文本样式,单击此处编辑母版标题样式,单击此处编辑母版文本样式,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,单击此处编辑母版标题样式,单击此处编辑母版文本样式,4.3,角,4.3.2 角的比较与运算,第四章 几何图形初步,4.3 角4.3.2 角的比较与运算第四章 几何图形初,新课导入,这节课我们学习角的大小比较与运算,.,你会比较这两个角的大小吗？,新课导入 这节课我们学习角的大小比较与运算.你,推进新课,角的比较,知识点,1,问题,怎样比较两个角的大小呢？,可以类比比较线段大小的方法,.,推进新课角的比较知识点1问题 怎样比较两个角的大小呢？可以,a,度量法.,B,A,C,D,E,F,70,40,ABC,DEF,a度量法.BACDEF7040ABC DEF,b,叠合法.,步骤,1,使两个角的顶点及一边,重合,；,2,两个角的另一边落在重合一边的,同侧,；,3,由两个角的另一边的位置确定两个角的大小,.,b叠合法.步骤1使两个角的顶点及一边重合；2两个角的另一边落,E,A,C,O,B,D,1.,如果,EC,与,OD,重合，那么,AEC,等于,BOD,，记作,AEC,BOD.,EACOBD1.如果EC与OD重合，那么AEC等于BO,E,A,C,O,B,D,2.,如果,EC,落在,BOD,的内部，那么,AEC,小 于,BOD,，记作,AEC,BOD.,EACOBD2.如果EC落在BOD的内部，那么AEC小,O,B,D,E,A,C,3.,如果,EC,落在,BOD,的外部，那么,AEC,大于,BOD,，记作,AEC,BOD.,OBDEAC3.如果EC落在BOD的外部，那么AEC大,思考,图中共有几个角？它们之间有什么关系？,图中共有,个角.,3,思考 图中共有几个角？它们之间有什么关系？图中共有,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,AOC,是,AOB,与,BOC,的,.,记作,AOC,=,；,AOB,是,AOC,与,BOC,的,，记作：,AOB,=,；类似地，,BOC,=,.,和,AOB,+,BOC,差,AO,C,-,BOC,AO,C,-,A,O,B,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,探究,利用一副三角板，你能画出哪些度数的角？这些角有什么规律？,都是,15,的倍数,.,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,问题,如图，如果,AOB,BOC,，那么,AOC,2,AOB,2,，,AOB,BOC,.,我们把射线,OB,叫做,AOC,的,角平分线,.,BOC,AOC,问题 如图，如果AOBBOC，那么AOC2AO,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,从一个角的顶点出发，把这个角分成相等的两个角的射线，叫这个,角的平分线,你能类比线段中点的定义，你能给角平分线下定义吗？,提问,答案,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,角的三等分线,角的四等分线,角的三等分线角的四等分线,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,角的运算,知识点,2,例,1,如图，,O,是直线,AB,上一点，,AOC,=53,17,，,求,BOC,的度数,.,分析：,AOB,是,，,BOC=,.,平角,AOB-,AOC,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,解：,由题意可知，,AOB,是平角，,AOB,AOC,BOC,所以,BOC,AOB,AOC,180,53,17,126,43.,解：由题意可知，AOB是平角，AOBAOCBOC,例,2,把一个周角,7,等分，每一份是多少度的角（精确到分）,?,解：,360,7,51,+3,7,51,+1807,51,26.,答：,每份是,51,26,的角,.,例2 把一个周角7等分，每一份是多少度的角（精确到分）?解,将余数的度数乘以60化成分.,360,7=51,+3,7=51,+1807,=51,+25+57=51,25+3007=51,2543,例2中，是怎样将剩余的度数化成分的？如果用精确到秒来表示计算的结果，答案是多少呢？,提问,答案,将余数的度数乘以60化成分.例2中，是怎样将剩余的度数化成分,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,随堂演练,1.,按图填空：,(,1,),AOB,+,BOC,=,；,(2),AOC,+,COD,=,；,(3),BOD,-,COD,=,；,(4),AOD,-,=,AOB,.,AOC,AO,D,B,O,C,B,O,D,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,课堂小结,角,比较,运算,度量法；叠合法,.,度与度、分与分、秒与秒分别相加、减,.,分秒相加时逢,60,要进位，相减时借,1,作,60.,状元成才路状元成才路状元成才路状元成才路状元成才路状元成才路,1.,从课后习题中选取；,2.,完成练习册本课时的习题。,课后作业,1.从课后习题中选取；课后作业,