“角的度量”是“垂线与平行线”单元的教学难点之一。学生之所以感到困难,主要的原因有三个:一是日常生活中很少有测量角度的现实需求,学生几乎没有测量角度的经历和经验;二是量角器的构造相对复杂,既有内圈刻度又有外圈刻度,而且刻度线通常又是断开的,学生很难从中看出作为度量单位的角;三是实际测量时还会遇到各种角的变式图形,需要对量角器的摆放位置进行合理灵活的调整,这 “Angle measurement ” is one of the teaching difficulties of “vertical and parallel lines ” unit. There are three main reasons why students find it difficult: First, there are few practical needs in daily life. Students have little experience and experience of measuring angles. Second, the structure of protractor is relatively complicated. There are outer ring scale, and the scale is usually off again, students can hardly see the angle as the unit of measure; Third, the actual measurement will encounter all kinds of angle variant graphics, the need for the placement of protractor Location of a reasonable and flexible adjustment, this