2020秋五E课堂苏教版数学五年级上册课件8.6 钉子板上的多边形.ppt

认识图形（二） 认识平面图形 认识图形（二） 认识平面图形 认识图形（二） 认识平面图形 苏教版 数学 五年级 上册 钉子板上的多边形 情境导入 活动探究 课外活动 活动课 拓展延伸 绿色中小学教育http://www.LSPJY.com 绿色圃中学资源网http://cz.L 绿色中小学教育http://www.LSPJY.com 绿色圃中学资源网http://cz.L 情境导入 想一想，钉子板上的多边形的面积可能跟什么有关？ ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ?● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1㎝ 1㎝ 数一数，下面图形的面积是多少？ 活动探究 1 9 10 厘 米 1 1厘米 ? ? ? ? 每个多边形边上的钉子各有多少？填入下表。 绿色中小学教育http://www.LSPJY.com 绿色圃中学资源网http://cz.L 绿色中小学教育http://www.LSPJY.com 绿色圃中学资源网http://cz.L ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1㎝ 1㎝ ① ② ③ ④ 图形编号 多边形的面积/平方厘米 多边形边上的钉子数/枚 ① ② ③ ④ ● ● ● 2 ● 4 ● ● ● ● ● 3 3.5 6 7 4 8 、●、 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 观察表格，你有什么发现？ ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ? ? ? ? 这些多边形，边上的钉子数越多，面积就越大。 这些多边形面积的平方厘米数是它们边上钉子数的一半。 图形①边上钉子数是4，面积是2平方厘米；图形②…… 图形编号 多边形的面积/平方厘米 多边形边上的钉子数/枚 ① 2 4 ② 3 6 ③ 3.5 7 ④ 4 8 (s) (n) S=n÷2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ? ? ? ? 图形内部只有1枚钉子。 这些图形还有什么特点？ 图形编号 多边形的面积/平方厘米 多边形边上的钉子数/枚 ① 2 4 ② 3 6 ③ 3.5 7 ④ 4 8 (s) (n) ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 1㎝ 1㎝ ① ② ③ ④ ● ● ● ● ● ● ● ● ● 、●、 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 图形中间 点的个数 用a来表示。 当a=1时，S=n÷2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●