# 抛 物 线 ( 一 ) - PowerPoint PPT Presentation

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(1)当0<e<1是椭圆；

（2）当e>1时是双曲线；

（3）那么当e=1时它是什么曲线 ？

y

y

y

y

F

K

0

K

F

x

0

0

0

x

x

x

F

K

K

F

y2=2px (p＞0)

y2=-2px (p＞0)

x2=2py (p＞0)

x2=-2py (p＞0)

（1）过点Q（-3，2）.

(2) 焦点在直线x-2y-4=0.

（3）焦点在y轴上，过点A（m，-3），到焦点的距离为5.

y2=16x ,x=-4或x2=-8y,y=2

y2= -8x，y=2

(2)曲线C上任一点到定点A（1，0）与到定直线x=4的距离之和等于5，求曲线C的轨迹方程,并说明是什么曲线？

y2=4x或y=0 (x<0)

4

2.过抛物线y2=-x的焦点F的直线交抛物线于A、B,且A、B在直线x= 上的射影分别是M、N，则∠MFN=

（ ）

A.450 B.600

C.900 D.以上都不对

C

3.抛物线y=x2上一点到直线2x-y-4+0的距离最短的坐标是————

(1,1)

1.本节复习了抛物线的定义及标准方程；

2.求抛物线方程的方法；

3.抛物线的几何性质及应用.