几何初步知识是教学的难点,在学生形成初步的空间观念的过程中,通过操作和演示,让学生动手、动口、动脑,有助于学生形成清晰的几何初步概念。下面介绍几个教学片断。 一、教学三角形的内角和 1、剪拼演示。让学生将自己准备的三角形的三个内角剪下,拼成一个平角,得知三角形的内角和是180°。如图 The preliminary knowledge of geometry is a difficult point in teaching. Through the operation and demonstration, students can form a clear initial concept of geometry through the operation and demonstration of students' hands, mouths and brains. Here are a few teaching pieces. First, the teaching triangle angle and 1, cut spell demonstration. Have the students trim the three inner corners of the triangle they prepared and make a flat angle, knowing that the interior angle of the triangle is 180 °. As shown