The locus of the mid-point of the chords of the circle `x^2+y^2=4` which subtends a right angle at the origin is `x+y=2` 2. `x^2+y^2=1` `x^2+y^2=2` `x+y=1`

Explanation

`/_OAD` and`/_OBD`

OA=OB

OD=OD

AD=DB

`/_OAD cong /_OBD`

`/_AOD=/_BOD=90/2=45`

`cos45=(OB)/(OA)`

`1/sqrt2=sqrt(h^2+k^2)/2`

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