Locus of mid point of chord AB of a circle `x^2 + y^2 = 4` which subtends `90^@` angle (1,0)

The locus of the midpoint of the chord of the circle x^2 + y^2 =4 which subtends a right angle at the origin is?

Locus of midpoint of chord of circle x^(2)+y^(2)=1 which subtend right angle at (2,-1) is

The locus of the midpoint of a chord of the circle x^(2)+y^(2) = 4 which subtends a right angle at the origin is

The locus of the midpoints of chords of the circle x^(2) + y^(2) = 1 which subtends a right angle at the origin is

The locus of the mid point of a chord of the circle x^(2)+y^(2)=4 which subtends a right angle at the origin is

The locus of the mid-points of chords of the circle x^2+y^2 =4 , which subtend a right angle at the origin, is: