有一些涉及直角三角形的问题,常常需要通过建立各种数学“模型”来解决,这是一种十分重要的思想方法.现举例说明.模型1如图1,在RtABC中,∠C=90°,∠ADC=60°,∠B=45°,BD=10,求AC的长.说明此类问题的特征是:具有公共直角的两个直角三角形,并且它们均位于直角边的同侧.解法1在AD There are some problems involving right-angled triangles, which often need to be solved by establishing various mathematical “models”. This is a very important method of thinking. Here is an example. Model 1 is shown in Figure 1. In RtABC, ∠C=90° ∠ ADC = 60°, ∠B = 45°, BD = 10, find the length of the AC. The characteristic of this type of problem is that there are two right-angled triangles with a common right angle, and they are all on the same side of the right-angled edge. 1 in AD