Circle 5 Question 9

9. The chords of contact of the pair of tangents drawn from each point on the line 2x+y=4 to the circle x2+y2=1 pass through the point… .

(1997, 2M)

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Answer:

Correct Answer: 9. 12,14

Solution:

  1. A point on the line 2x+y=4 is of the form (h,42h).

Equation of the chord of contact is T=0 i.e.

hx+(42h)y=1(4y1)+h(x2y)=0

This line passes through the point of intersection of 4y1=0 and x2y=0 i.e. through the point 12,14.



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