高二英语人教版必修5课件：unit 1 reading task .ppt

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1、人教课标高二必修5Unit1ReadingtaskonPage44Unit1GreatscientistsWhat’sEuler’spuzzle?Koningsbergisanislandandthereisariverbreakingitintotwoparts.“SevenBridgesofKonigsberg”andthefamous“Eulerpath”.Peoplewonderediftheycouldwalkaroundthecitybycrossingthesevenbridgeswithoutgoingoveranyofthemtwiceo

2、rgoingbackonhimself,butEulerfoundhecouldn’tcrossallthesevenones.ThisisEuler’spuzzle.Thefirststageinhisresearchistofindtheproblemthathecouldcrosssixofthebridgeswithoutgoingoveranyofthemtwiceorgoingbackonhimself,buthecouldn’tcrossallseven.HowdidEulerprepareforhisresearch?Thesecondsta

3、geistothinkofamethod:Hedrewamapanduseddotsandlinestosimplifyhisanalysis.Tryingandobservingoverandoveragain,hefoundageneralrule.Itistopology.Euler’stheoryiscalled“TheEulerpath”,whichisexpressedlikethis:Ifafigurehasmorethantwooddpoints,youcannotgooveritwithoutliftingyourpencilfromthe

4、pageorgoingoveralinetwice.Whatarethetheories?SothegeneralrulethatEulerfoundistheevenpointsandtheoddpoints.Lookatthefollowingpictures:ConclusionEuler’stheory(一笔画)可以一笔画只有两种情况：1.没有奇数顶点。2.只有两个奇数顶点。