Find The Condition That Chord Of Contact Of Any External Point (h, k) To The Circle x2 + y2 = a2 should Subtend Right Angle At The Centre Of The Circle.

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Find the condition that chord of contact of any external point

(hk) to the circle x2 + y2 = a2 should subtend right angle at the centre of the circle.


Correct option is


Equation of chord of contact AB is  

             hx + ky = a2            …(1)

for equation of pair of tangent of OA and OB, make homogeneous x2 +y2 = a2 with the help of hx + ky = a2 or    







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