“几何图形初步”中的有关知识是平面几何的基础内容,学好这部分知识可以为学好平面几何奠定基础.在学习“几何图形初步”这部分知识的过程中,有些同学由于对有关知识理解不清,运用时常出现这样或那样的错误,现对其中一些典型错误加以剖析,希望能引起同学们的注意.一、概念不清例1判定正误,对错误的加以改正.(1)在∠ABC的一边的延长线上取一点D; The related knowledge in “Preliminary of Geometry” is the basic content of plane geometry, learning this part of knowledge can lay a solid foundation for studying plane geometry.In the process of learning “Geometry Preliminary Part,” some students, The understanding of knowledge is unclear, the use of such and such errors often appear, some of them are now typical errors to be analyzed in the hope of arousing the students’ attention. First, the concept is not clear Example 1 is correct, correct the error. ) Take a point D on the extension of ∠ABC;