八年级数学下册 2.2_全等三角形的识别课件 华东师大版 课件VIP专享VIP免费

Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPRO全等三角形的条件( 一 )Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPRO温故知新：1 、全等三角形定义和性质2 、我们学过几种判定两个三角形全等的条件？Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPRO探究 1 ：先任意画出一个△ ABC ，再画出一个△ A1B1C1 ，使 A1B1=AB,A1C1=AC, A1= A （即有两边和它们的夹角对应相等）把画好的△ A1B1C1 剪下，放到△ ABC 上，它们全等吗？Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPRO做一做： 画一个三角形，使它的一个内角为 60 度，夹这个角的一条边为 6 厘米，另一条边长为5 厘米 .Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPROABCA’MNCB’′′Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPRO总结：三角形全等的条件（ 1 ）（简记为 SAS 或边角边 )ABCA1B1C1如果两个三角形的两边及夹角分别对应相等 , 那么这两个三角形全等 .Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPROAB = A1 B1 A ∠= A∠1 AC = A1 C1 ∴△ ABC A≌ △1 B1 C1 （ SAS ）在△ ABC 和△ A1B1C1 中ABCA1B1C1Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPROⅠ8930oⅤ8530oⅥ8830o8930o Ⅶ8830oⅢⅣ 85Ⅷ855Ⅱ30o8比眼力：找全等。Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPROABDC例：如图：在△ ABC 中 , AB = AC, AD 平分∠ BAC, 求证 :ΔABDΔACD≌Presented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPRO若 AB=AC则添加什么条件可得 ΔABDΔACD≌ADBCPresented ByPresented ByHarry Mills /Harry Mills / PRESENTATIONPRO PRESENTATIONPRO立竿见影已知 : 点 M 是等腰梯形 ABCD 底边 AB 的中点 ,求证 :AMD BMC△≌ △ ACDBMPresented ByPresented ByHarry Mills /Harry Mills / PRESENTATI...