过椭圆的左焦点F且倾斜角为60度的直线交椭圆于A,B两点,若 FA=2FB ,则椭圆的离心率为_______请问不用准线要怎么求啊?老师说准线在高考中不作要求的.还有,为什么|AT| = |AC| - |BD| = x/e
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/04 02:43:21
![过椭圆的左焦点F且倾斜角为60度的直线交椭圆于A,B两点,若 FA=2FB ,则椭圆的离心率为_______请问不用准线要怎么求啊?老师说准线在高考中不作要求的.还有,为什么|AT| = |AC| - |BD| = x/e](/uploads/image/z/8820281-65-1.jpg?t=%E8%BF%87%E6%A4%AD%E5%9C%86%E7%9A%84%E5%B7%A6%E7%84%A6%E7%82%B9F%E4%B8%94%E5%80%BE%E6%96%9C%E8%A7%92%E4%B8%BA60%E5%BA%A6%E7%9A%84%E7%9B%B4%E7%BA%BF%E4%BA%A4%E6%A4%AD%E5%9C%86%E4%BA%8EA%2CB%E4%B8%A4%E7%82%B9%2C%E8%8B%A5+FA%3D2FB+%2C%E5%88%99%E6%A4%AD%E5%9C%86%E7%9A%84%E7%A6%BB%E5%BF%83%E7%8E%87%E4%B8%BA_______%E8%AF%B7%E9%97%AE%E4%B8%8D%E7%94%A8%E5%87%86%E7%BA%BF%E8%A6%81%E6%80%8E%E4%B9%88%E6%B1%82%E5%95%8A%3F%E8%80%81%E5%B8%88%E8%AF%B4%E5%87%86%E7%BA%BF%E5%9C%A8%E9%AB%98%E8%80%83%E4%B8%AD%E4%B8%8D%E4%BD%9C%E8%A6%81%E6%B1%82%E7%9A%84.%E8%BF%98%E6%9C%89%2C%E4%B8%BA%E4%BB%80%E4%B9%88%7CAT%7C+%3D+%7CAC%7C+-+%7CBD%7C+%3D+x%2Fe)
过椭圆的左焦点F且倾斜角为60度的直线交椭圆于A,B两点,若 FA=2FB ,则椭圆的离心率为_______请问不用准线要怎么求啊?老师说准线在高考中不作要求的.还有,为什么|AT| = |AC| - |BD| = x/e
过椭圆的左焦点F且倾斜角为60度的直线交椭圆于A,B两点,若 FA=2FB ,则椭圆的离心率为_______
请问不用准线要怎么求啊?老师说准线在高考中不作要求的.
还有,为什么|AT| = |AC| - |BD| = x/e
过椭圆的左焦点F且倾斜角为60度的直线交椭圆于A,B两点,若 FA=2FB ,则椭圆的离心率为_______请问不用准线要怎么求啊?老师说准线在高考中不作要求的.还有,为什么|AT| = |AC| - |BD| = x/e
设A和B在左准线上射影分别为C和D,|FB| = x,
作BT⊥AC于T,则有|AT| = |AC| - |BD| = x/e
|AB| = |AF| + |BF| = 3x,在直角三角形ABT中有:
|AT| = |AB|cos 60°,即x/e = 3x/2.
所以离心率e = 2/3.