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本文将近几年高考对平面几何选讲部分常考题型及解析总结如下,供备考学生参考.类型一:与圆的切割线有关的求线段长度问题例题1(2013年高考重庆数学(理))如图1,在△ABC中,∠C=90°,∠A=60°,AB=20,过C作△ABC的外接圆的切线CD,BD⊥CD,BD与外接圆交于点E,则DE的长为.解析本题考查与圆有关的几何证明问题.延长BA交切线CD于M因为∠C=90°,所以AB为直径,所以半径为10.连结OC,则OC
In this paper, college entrance examination in recent years on the geometric selection of plane geometry part of the common test questions and analytical summary is as follows, for the test students reference type one: with the circular cutting line to find the length of the line Example 1 (2013 college entrance examination in Chongqing Mathematics (Li) As shown in Figure 1, △ ABC, ∠C = 90 °, ∠A = 60 °, AB = 20, C for the ABC of the circumcircle of the tangent of the CD, BD⊥CD, BD and the circumcircle intersect at point E, Then the DE is long.Analyzing the problem of examining the circle with the geometric proof.Extended BA intersecting line CD in M because ∠C = 90 °, so AB is the diameter, so the radius is 10.Connected OC, OC