If the locus of midpoints of the chords of the circle
\[
S\equiv x^2+y^2-6x-8y-11=0
\]
which subtend a right angle at \(A(1,2)\) is another circle \(S'=0\), then the centre of \(S'=0\)
Show Hint
For a fixed point \(P\), the locus of the midpoints of the chords of a circle subtending a right angle at \(P\) is another circle whose centre is the midpoint of the line joining \(P\) and the centre of the given circle.