Question: ab is any chord of the circle?
Answer: AB is any chord of the circle x2+y2-6x-8y-11=0 which subtends an angle π2 at (1,2). If locus of midpoint of AB is a circle x2+y2-2ax-2by-c=0; then find the value of (a+b+c). a+b+c=3+4-17=-10.