lf the area of the quadrilateral formed by the tangent from the origin to the circle x2+y2+6x−10y+c=0 and the pair of radii at the points of contact of these tangents to the circle is 8 square units, then c is a root of the equation
A
c2−32c+64=0
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B
c2−34c+64=0
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C
c2+2c−64=0
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D
c2+34c−64=0
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Solution
The correct option is Bc2−34c+64=0 AC=AB= Length of tangent from (0,0) to S:x2+y2+6x−10y+c=0 AC=AB=√S1=√c Area of quadrilateral ABOC= Area of △ABO+ Area of △ACO =12×AB×r+12×AC×r
=r2[√c+√c] =r√c Given : r√c=8 √34−c×√c=8 ⇒34c−c2=64 ⇒c2−34c+64=0