遇中点如何添加辅助线?常见的有作三角形的中位线,作直角三角形斜边的中线,还可以加平行线构造“■”字形的全等三角形.本文针对最后一种方法列举两例,供读者参考.例1如图1,在△ABC中,,∠A=45°,延长CB至点D使BD=BC.(1)若∠ACB=90°,求证:BD=AC;(2)如图2,分别从点D和点C作AB所在直线的垂线,垂足分别为E、F,求证:DE=CF; In the midpoint of how to add auxiliary line? Common with the median line of the triangle, the hypotenuse of the right triangle center line, you can also add parallel lines to construct “ ” congruent triangle shape.This article lists the last method Two cases, for readers reference .Example 1 As shown in Figure 1, △ ABC ,, ∠A = 45 °, extending CB to point D BD = BC. (1) If ∠ ACB = 90 °, verify: BD = AC ; (2) as shown in Figure 2, respectively, from point D and point C for AB where the vertical line, the foot is E, F, verify: DE = CF;