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我们在做几何题目时,往往要作辅助线.作什么样的辅助线,要根据具体的条件.比如直角三角形中,出现了斜边的中点,我们会想到作斜边的中线;三角形中出现了两边的中点,我们会想到作中位线;出现30°、45°、60°的角,我们会想到作垂直构造直角三角形;出现圆的切线,我们会想到把圆心和切点连接起来,得到垂直……那什么条件下,应该作圆呢?来看看下面几种情况.一、遇到旋转构造圆例1如图1,正方形ABCD的边长为4cm,正方形AEFG的边长为1cm.如果正方形AEFG绕点A旋转一周,设C、F两点之间
When we do geometric problems, we often need to make auxiliary lines, and what kind of auxiliary lines should be based on specific conditions, such as right-angled triangles, where the mid-point of the hypotenuse appears, and we will think of the middle line as hypotenuse; We’ve got the mid-point on both sides, and we’ll think of mid-line. With angles of 30 °, 45 °, and 60 °, we’ll think of a right-angled triangle for vertical construction. With the tangent to the circle, we’ll think of connecting the center of the circle to the tangent point Up, get vertical ... ... Under what conditions should be round it? Take a look at the following situations. First, encounter the rotation of the circle Example 1 Figure 1, the side of the square ABCD is 4cm, the side of the square AEFG 1cm. If the square AEFG around A point of a rotation, set C, F between two points