Chapter 10.6, Problem 4QCE

If the distance from a vertex of a hyperbola to the nearest focus is $r_0,$ and if the distance from that vertex to the farthest focus is $r_1,$ then the semifocal axis is $a=\text{\_\_\_\_\_}$ and the semiconjugate axis is $b=\text{\_\_\_\_\_}\text{.}$