焦准距
focal distance The distance from the focus to the directrix, usually denoted by $p$ ($p > 0$). In the standard equation $y^2 = 2px$, $p$ is the focal distance.
CSCA 数学 考试术语
focal distance The distance from the focus to the directrix, usually denoted by $p$ ($p > 0$). In the standard equation $y^2 = 2px$, $p$ is the focal distance.
CSCA 数学 考试术语