1) If one of the diameters of the circle x2+y2−2x−6y+6=0 is a chord to the circle with centre (2,1), then the radius of the bigger circle is A) 6 B) 4 C) 2 D) 3 Answer: Option DExplanation:Equation of circle x2+y2−2x−6y+6=0 Centre (1,3) ,r= √1+9−6=2 OA = √(2−1)2+(1−3)2⇒OA=√1+4=√5 ∵ AB= r=2 and R2=r2+OA2 ⇒ R2=4+5⇒ R=3