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和三角形、四边形相比,圆这部分知识显得综合性比较强,与所学知识联系较大,所以,学生往往不会作辅助线或找不出最佳的证明方法.经过多年的教学实践,笔者总结出在解决圆的有关问题时常用到如下几种作辅助线的方法:1.有弦,可作弦心距.2.有切线,可连过切点的半径.3.有直径,可作直径上的圆周角或作同弧或等弧所对的圆周角.4.两圆相交时可连结公共弦.
Compared with triangles and quadrilaterals, this part of the circle seems to be relatively comprehensive and has a lot to do with the knowledge it learns. Therefore, students often do not act as auxiliary lines or find the best way to prove them. After many years of teaching practice, The author concludes that in the solution of round related problems often used as the following several methods for the auxiliary line: 1. Strings, can be used for the chord distance 2. There is a tangent, you can even cross the tangent point radius 3. With diameter, For the diameter of the circumference of the circle or for the same arc or arc equivalent angle of the circle .4.