第8课时椭圆的定义与标准方程.ppt

武都八一中学;;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.;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.;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.;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.;Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.;?自然界处处存在着椭圆,我们如何用自己的双手画出椭圆呢?;?实验;?如何定义椭圆?; 1. 改变两图钉之间的距离，使其与绳长相等，画出的图形还是椭圆吗？; 1. 改变两图钉之间的距离，使其与绳长相等，画出的图形还是椭圆吗？; 平面内与两个定点F1、F2的距离的和等于常数（ ）的点的轨迹叫做椭圆。;回忆直接法求曲线方程的步骤;? 探讨建立平面直角坐标系的方案;x;两边除以 得;刚才我们得到了焦点在x轴上的椭圆方程， 如何推导焦点在y轴上的椭圆的标准方程呢？;;分母哪个大，焦点就在哪个轴上;则a＝ ，b＝ ；;例1.求下列椭圆的焦点坐标，焦距，以及椭圆上每一点到两焦点距离的和。;例2.求适合下列条件的椭圆的标准方程。;求椭圆方程的方法：（待定系数法） 第一步：根据条件确定焦点所在位置设出方程 第二步：计算参数a和b 第三步：写出方程;例3、若一椭圆两焦点分别是椭圆 9x2+4y2=36的两焦点，并且经过点A(2,?3)，求该椭圆方程.; [解] ∵椭圆9x2+4y2=36的两焦点;Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.;小结：;分母哪个大，焦点就在哪??轴上;探索－嫦娥奔月;作业：;再见！