Given A≡(1,1) and AB is any line through it cutting the x -axis at B . If AC is perpendicular to AB and meets the
y -axis in C , then the equation of the locus of midpoint Pof BC is
x+y=1
x+y=2
x+y=2xy
2x+2y=1
The equation of line AB is y−1=m(x−1) . Therefore, the equation of line AC is
y−1=−1m(x−1)
2h=1−1m2k=1+1m
Eliminating m , we have locus x+y=1 .