高中数学，椭圆上的一点与与两个焦点有什么关系，同理，双曲线呢 椭圆与双曲线的区别和联系，椭圆的abc分别指什么，双曲线的a...
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双曲线：双曲线上任意一点到两焦点连线的差等于2a表达式：x^2/a^2-y^2/b^2=1
令这点为P焦点为F与D
椭圆为【PF】＋【PD】=2a
双曲线为【PF】－【PF】=2a
【】指向量的绝对值
图形上的点到两焦点距离和是定长
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