数学探究是数学新课程标准提倡的数学学习的一种新的方式。数学探究课题的选择是实现探究学习的关键 ,现运用运动变化的观点 ,围绕一道课本习题作一些探究。人教版《几何》课本的第 1 2 9页 ,例 4是一个涉及切点三角形的题。题　如图 ,⊙O1和⊙O2 外切于点A ,BC是两圆的外公切 Math inquiry is a new way of mathematics learning advocated by the new mathematics curriculum standards. The choice of the topic of mathematics inquiry is the key to the realization of inquiry learning. Now we use the viewpoint of movement change to make some explorations around a textbook exercise. For example, page 1 of page 2 of the textbook “Geometry” of People’s Education Press, Example 4 is a question involving cut-point triangles. As shown in the figure, ⊙O1 and ⊙O2 are circumscribed at point A, and BC is a circle with two male characters.