焦距
focal distance The distance from the center of the ellipse to a focus, usually denoted by $c$, satisfying $c^2 = a^2 - b^2$.
CSCA 数学 考试术语
focal distance The distance from the center of the ellipse to a focus, usually denoted by $c$, satisfying $c^2 = a^2 - b^2$.
CSCA 数学 考试术语