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等积法是初中数学中常见的一种解题方法,利用这一方法解决某些问题,能化难为易,化繁为简,下面举例供参考。一、求三角形的高例1(2014年贺州中考题)网格中的每个小正方形的边长都是1,△ABC每个顶点都在网格的交点处,则sinA=____.解析如图1,作AD⊥BC于点D,CE⊥AB于点E,由勾股定理,得AB=AC=25~(1/2),BC=22~(1/2),AD=32~(1/2).由1/2BC·AD=1/2AB·CE,
Equivalence method is a common method of solving problems in junior high school mathematics. It is difficult to make things easier and easier to use by this method. The following examples are for reference. First, find a high triangle 1 (2014 HE state entrance exam) Each small square in the grid side length is 1, △ ABC each vertex at the intersection of the grid, then sinA = ____. Figure 1, AD ⊥ BC at point D, CE ⊥ AB at point E by the Pythagorean theorem, AB = AC = 25 ~ (1/2), BC = 22 ~ (1/2). By 1 / 2BC · AD = 1 / 2AB · CE,