Given in $3D$ ellipsoid semi-major axis $a=5$, $b =4$ and $c=3$ . How can we find the distance $D$ between two focal points: $F_1$ and $F_2$? Also how can I find the distance from focal point $F_1$ or point $P$ to $S$ ? Will the distance from ($F_1 \rightarrow S$) + ($S \rightarrow F_2$) be equal to $2a$ like an ellipse ?
