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6. 圆和角的关系这一项目的教学是研究了圆和一条直綫的位置关系、圆和圆的位置关系之后的进一步发展。这里包括着两个主要内容: 1)以圆周角的度量定理为基础来说明和圆有关的角的度量定理; 2)应用这些定理来解的几个重要作图题——圆的切线,两圆的公切綫,在已知綫段上作含有已知角的弓形。在教学中首先要使学生掌握“与圆有关的角”这一概念。教师可以先向学生指出,在研究了圆和一直綫的位置关系后,现在进一步来研究圆和两条直綫的位置关系。由此领导学生进行以下的分析: 1)两条直綫本身的位置关系有两种可能:
6. The relationship between circle and angle The teaching of this project is to study the further development after the positional relationship between the circle and a straight line, and the positional relationship between the circle and the circle. Here are two main contents: 1) Measure the theorem of the angle related to the circle based on the theorem of the measurement of the circumferential angle; 2) Apply some of these theorems to solve several important questions - the tangent of the circle, two The round common tangent, on the known line segment, has a bow with a known angle. In teaching, we must first make students master the concept of “corners related to the circle.” The teacher can point out to the student first, after studying the position relation of the circle and the straight line, now further study the positional relationship between the circle and the two straight lines. This leads the students to the following analysis: 1) There are two possibilities for the positional relationship between the two straight lines: