在一些基本图形中,蕴含着许多有用的知识,如果同学们细心思考、仔细玩味,就会有意想不到的惊喜和收获.现举一例说明:例如图1所示,在△ABC中,AB=AC=13,BC=10,D是AB的中点,过点D作DE⊥AC于点E,则DE的长是.思路点拨△ABC是等腰三角形,常常用到勾股定理.D是AB的中点,遇中点要想到中位线.过B作BG⊥AC于G,BG可利用△ABC面积不变来求得.由等腰三角形中三线合一及勾股定理知BC上的高AF In some basic graphics, contains a lot of useful knowledge, if students think carefully, pondering carefully, there will be unexpected surprises and gains.For example: As shown in Figure 1, △ ABC, AB = AC = 13, BC = 10, D is the midpoint of AB, the point D for DE⊥AC at point E, then the DE is long. Idea point △ △ ABC is the isosceles triangle, the Pythagorean theorem is often used. D is AB Of the middle point, in the middle to think of the median line. B for BG⊥AC in G, BG can be used to obtain the same △ ABC area. By the isosceles triangle and Pythagorean theorem know BC High AF