利用定义求圆锥曲线轨迹方程.ppt

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1、例2．求和圆O:x2+y2=1外切，且和直线x=-1相切的动圆圆心C的轨迹方程。设：动圆圆心C（x,y)，半径为r。解：xyO。C则有

2、OC

3、=r+1而r=

4、x+1

5、从而得

6、OC

7、=

8、x+1

9、+1化简得：当x>-1时，y2=4(x+1)当x<-1时，y=0从一道例题引发的思考:想没想过考虑直线l:x=-2?Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd

10、.“定义法”求轨迹方程圆锥曲线专题复习1Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.所以，动圆心的轨迹是以O1、O2为焦点，2a=12的椭圆Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd."定义法

11、"求轨迹方程的一般步骤:一定型二定位三定方程四定范围Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.（点F不在l上）Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.在平面内,讨论：圆椭圆除去长轴两端点

12、双曲线的右支抛物线Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.OxyQPF1F2AEvaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.OxyQPF1F2Evaluationonly.Createdwi

13、thAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyri

14、ght2004-2011AsposePtyLtd.小结定义法求轨迹一定型椭圆双曲线抛物线圆二定位三定方程四定范围射线Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.