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 of (hk)  

               xh + yk = a2                …(i)

Taking the equation of circle x2 + y2 – a2 = 0 

Homogeneous with the help of xh + yk = a2



Sub tent 90o at the origin so   


∴ Coefficient of x2 + Coefficient of y2 = 0    





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The chord of contact of tangents drawn from a point on the circle x2 +y2 = a2 to the circle x2 + y2 = b2 thouchese x2 + y2 = e2 find ab in.