If A and B are two fixed points, then the locus of a point which moves in such a way that the angle APB is a right angle, is

Let A x1 , y1 , B  x2  ,y2  be two fixed points andlet P ( h, k )  be a variable point such that  ∠APB=π2⋅ Then, Slope of AP× Slope of BP = -1⇒ h−x1h−x2+(k−y/1)k−y2=0Hence, the locus of  ( h, k ) is  x−x1x−x2+y−y1y−y2=0 which is a circlehaving  AB  as diameter