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“圆”这一章中概念、定理(性质)较多,图形位置关系复杂,学生们在解题时常常出现这样或那样的错误,现举几例,加以剖析,以期有所帮助。一、概念模糊或忽视定理、性质成立的条件例1:不少学生误认为下列假命题为真命题。①长度相等的弧是等弧;②过三点确定一个圆;③平分弦的直径垂直于弦;④顶点在圆周上的角叫圆周角;⑤圆心角的度数等于圆周角度数的2倍;⑥垂直于半径的直线是圆的切线。
There are many concepts, theorems (nature) in the chapter of “circle”, and the positional relationship of graphs is complex. Students often have such mistakes or errors in solving problems. Here are a few examples to be analyzed to help them. First, the concept of fuzzy or neglect theorems, the conditions of the establishment of the conditions Example 1: Many students mistakenly believe that the following false propositions are true propositions. 1 equal length of the arc is equal to the arc; 2 to determine a circle through three points; 3 the diameter of the chord is perpendicular to the chord; the angle of the 4 vertices on the circumference is called the circumference angle; 5 degrees of the circle angle is equal to 2 times of the circumference angle; 6 The line perpendicular to the radius is the tangent of the circle.