一般地,若平面上的一个动点P满足条件P(S),则P的轨迹是曲线C={P|P(S)}.问题是曲线C是怎样的曲线呢?这需要从条件P(S)出发做进一步的探究.有时直接由条件P(S)作图,观察轨迹;有时从几何条件转化,化归为某个已经学过的曲线;有时建立坐标系,先获得轨迹方程,再通过方程研究轨迹.后者就是解析几何中轨迹探究的一般策略. In general, the trajectory of P is the curve C = {P | P (S)} if a moving point P on the plane satisfies the condition P (S). The question is what curve C is? (S) for further exploration sometimes plot directly from the conditions of P (S), to observe the trajectory; sometimes transformed from geometric conditions, into a curve already learned; and sometimes the establishment of coordinate system, first get the trajectory equation, Then we study the trajectory through the equation, which is the general strategy of trajectory exploration in analytic geometry.