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Questions  

The length of the tangent drawn from any point

on the circle   x2+y2+2gx+2fy+c=0 to the circle

x2+y2+2gx+2fy+c1=0 is 

a
c1⋯c
b
c−c1
c
c−c1
d
c1−c

detailed solution

Correct option is D

Let (α,β) be a point on  x2+y2+2gx+2fy+c=0 Then, the length of the tangent from  (α,β) tox2+y2+2gx+2fy+c1=0 is given by  l=α2+β2+2gα+2fβ+c1Since  (α,β) lies on  x2+y2+2gx+2fy+c=0  ∴ α2+β2+2gα+2fβ=−cHence l=c1−c

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