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Ask iit jee aieee pet cbse icse state board community Community Discussion Question: CIRCLES
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ashish_banga (984)

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IF TWO DISTINCT CHORDS, DRAWN FROM THE POINT (P,Q) TO THE CIRCLE   x2 + y2 = px + qy


( pq not equal to 0) ARE BISECTED BY X - AXIS, THEN FIND RELATION BETWEEN P AND Q

    
allamraju (3422)

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The ans is P2>8Q2.Posting the soln in next post,...

MAKING A MISTAKE IS HUMAN BUT REPEATING IT IS IDIOTIC.
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allamraju (3422)

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Since the chords drawn from (p,q) are bisected by X-axis,The midpoint of these chords is of the form (a,0) and hence the other extremity of the chord becomes (2a-p,-q).This lies on the circle iff (2a-p)2+q2=p(2a-p)-q2 iff 2a2-3ap+p2+q2=0

Now,this quadratic shud have two distinct roots as two distinct are bisected by x-axis,hance the discriminant 9p2-8(p2+q2)>0p2>8q2

MAKING A MISTAKE IS HUMAN BUT REPEATING IT IS IDIOTIC.
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karansingh (401)

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can u give the diagram
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heavensablaze (106)

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There is one more method to do this question.


 


that is by using the equation of the chord whose mid pt. is given  S1=T


 


let the mid pt be (a,0)


 


Therefore we get     a2-ap=ax -px/2 -ap/2 - qy/2


 


now since pt. (p,q) lies on chord we can satisfy the equation with it


 


a2-ap-ap+p2/2+ap/2+q2/2=0


 


2a2-4ap+p2+ap+q2=0


 


2a2-3ap+(p2+q2)=0


 


 


 


Now,this quadratic shud have two distinct roots as two distinct are bisected by x-axis,hance the discriminant D>0

 


 


 


9p2-8(p2+q2)>0

 


thus we get p2>8q2


 


Plz rate if the soln. was helpful.

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