辅助线在几何证题中起着桥梁作用和化难为易的作用,恰当地添加辅助线,可以帮我们开阔思路,把隐性条件明显化.也就是说,辅助线可以把已知条件与待解决的问题联系起来,从而找到解决问题的方法.一、造相似三角形法若要证角相等或线段成比例,通常利用相似三角形.如果没有现成的相似三角形,就需要作辅助线来创造.在构造三角形时,常常是按比例式选定三角形,然后从图形看形状是否相似,再作平行线,或者利用平行于三角形一边的直线 Auxiliary lines play a bridge role in the geometry of the problem and the role of the difficulty is easy, the appropriate addition of auxiliary lines, can help us broaden our thinking, the obvious hidden conditions. In other words, auxiliary lines can be known conditions and to be To solve the problem, to find a solution to the problem. First, the method of making similar to the triangle method to equal the angle or line segment is proportional to the usual use of similar triangles. If there is no ready-made similar triangles, you need to be auxiliary lines to create. When constructing triangles, it is common to choose triangles proportionately and then see if the shapes are similar from the shapes, then make parallel lines, or use lines that are parallel to one side of the triangle