Question 1016836
Line containing  (4,2) and (2,-1)  will have slope {{{-3/2}}}.


The bisected chord will be on the line of equation {{{y-(-1)=(2/3)(x-2)}}},
{{{y=(2/3)x-7/3}}}.


The points on the circle of the bisected chord will the the intersection points of {{{y=(2/3)x-7/3}}}  and {{{(x-4)^2+(y-2)^2=25}}}.  Use the distance formula to find the distance between these two points.