论文部分内容阅读
切线是直线与圆的位置关系中最重要的一种关系。随着新课改的推进,近几年的中考题中越来越多地出现了证明圆的切线的题型,为此,我在教学中积累了证明圆的切线的几道典型例题,每道题中都经典地用到了切线的判定定理,但方法各异。下面我介绍三道经典题。例1.在直角三角形ABC中,AC=3 cm,BC=4 cm,∠C=90°当r为2.4 cm时,以C为圆心,r为半径的圆与AB有何位置关系?
Tangential line is the relationship between the position of the circle and the most important relationship. With the advancing of the new curriculum reform, more and more questions of proving the tangent of the circle appear in the entrance exams of recent years. For this reason, I have accumulated a few typical examples in teaching that show the tangent of the circle. Questions are used in classic tangent judgment theorem, but the method is different. Here I introduce three classic questions. Example 1. In a right-angled triangle ABC, AC = 3 cm, BC = 4 cm, ∠C = 90 ° When r is 2.4 cm, what is the relation between a circle with radius r and AB?