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由图形中的一个或多个动点沿射线、线段或弧线运动,引起未知量与已知量间的一种变化关系,就是动点问题中的函数关系.这种函数关系是近年中考命题的热点,常见的有一次函数、二次函数,反比例函数等.解决这类问题的关键是动中求静,灵活运用有关数学知识解决问题.现举例解析如下.一、利用三角形的相似关系建立函数解析式例1(2010荆州)如图1,直角梯形OABC的直角顶点O是坐标原点,边OA,OC分别在x轴、y轴的正半轴上,OA∥BC,D是BC上一点,BD=1/4 OA=(?),AB=
By one or more moving point in the graph along the ray, line segment or arc motion, causing the unknown amount and the known amount of a change between the relationship is the function of the fixed point in the problem. This function is the relationship between the test in recent years Of the common, there is a common function, quadratic function, inverse proportion function, etc. The key to solve this kind of problem is moving in for static, flexible use of mathematical knowledge to solve the problem.Examples are as follows.First, the use of triangles to establish similarities Function Analysis Example 1 (2010 Jingzhou) Figure 1, right-angle trapezoid OABC vertex O is the origin of coordinates, while OA, OC respectively in the x-axis, y-axis of the positive semi-axis, OA∥BC, D is BC on the point , BD = 1/4 OA = (?), AB =