例例2求和圆求和圆O:x2+y2=1外切，且和直线外切，且和直线x=-1相切的动圆相切的动圆圆心圆心C的轨迹方程。的轨迹方程。 设：动圆圆心设：动圆圆心C（x,y)，半径为，半径为r。 解：xyO。C则有|OC|=r+1而r=|x+1|从而得|OC|=|x+1|+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从一道例题引发的思考: :想没想过考虑直线想没想过考虑直线l:x=-2 ?Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.“定义法”求轨迹方程圆锥曲线专题复习圆锥曲线专题复习1Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.所以，动圆心的轨迹是所以，动圆心的轨迹是以以O1、O2为焦点，为焦点，2a=12的的椭圆椭圆Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.一一 定定 型型二二 定定 位位三三 定定 方方 程程四四 定定 范范 围围Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.（点（点F不在不在l上）上）Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.在平面内在平面内 , ,讨论：讨论：圆圆椭圆椭圆除去长轴两端点双曲线的右支双曲线的右支抛物线抛物线Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.OxyQ QPF1F2AEvaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.OxyQ QPF1F2Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.小结小结定义法求轨迹定义法求轨迹一定型一定型椭圆椭圆双曲线双曲线抛物线抛物线圆圆二定位二定位三定方程三定方程四定范围四定范围射线射线Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.