一、故事导入,引发猜想师:什么叫三角形?生:由3条线段围成的图形叫三角形。(师板书:三条线段围)师:老师也围了一个三角形,这个三角形里还有故事呢?(课件出示:三角形图)师:猴哥哥和猴妹妹举行比赛,哥哥定好终点,并为自己选好红色的路线,猜猜看谁会赢?生:猴哥哥赢。(课件播放比赛过程)师:猴妹妹不服气,要改变规则!这次谁会赢呢?生:猴妹妹会赢。(课件播放第二次比赛过程) First, the introduction of the story, trigger guess Teacher: What is the triangle? Health: surrounded by three lines of graphics called the triangle. (Teacher’s book: three lines around) Teacher: the teacher also surrounded a triangle, there is a story in this triangle? (Courseware: triangle diagram) Teacher: monkey brother and sister held a contest, my brother set a good end, Good red line, guess who will win? Health: Monkey brother win. (Courseware player competition process) division: Monkey sister not convinced, to change the rules! Who will win this time? Health: Monkey sister will win. (Courseware playing the second game)