Let C be a circle with radius 10 units and centre at the origin. Let the line x + y = 2 intersect the circle C at the points P and Q. Let MN be a chord of C of length 2 unit and slope -1. Then, a distance (in units) between the chord PQ and the chord MN is
- 3 - 2
- 2 - 3
- 2 - 1
- 2 + 1
Answer
(1) 3 - 2
Solution
∵ distance of a chord from the centre = r2 - (half chord)2
PQ: x + y = 2 ⇒ distance from O = 2 2 = 2
MN (half-chord 1): distance from O = 10 - 1 = 3 ⇒ MN: x + y = 3 2
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Both chords have slope -1 (parallel) ⇒ distance = 3 - 2 (same side of O) or 3 + 2 (opposite side)
a distance = 3 - 2
Answer: (1)