Q.

Let C be a circle with radius 10 units and centre at the origin. Let the line x + y = 2 intersects the circle C at the points P and Q. Let MN be a chord of C of length 2 units and slope –1. Then a distance (in units) between the chord PQ and the chord MN is          [2024]

1 3–2  
2 2–3  
3 2+1  
4 2–1  

Ans.

(1)

Distance of centre from chord PQ =|0 + 0 –212 + 12|= 22 = 2

Let distance of centre from chord MN = p, then length of chord = 210 – p2

⇒    210 – p2 = 2            (∵   Given)

⇒    10 – p2 = 1   ⇒   p2 = 9   ⇒   p = 3

⇒    Distance between chord PQ and MN = 3 – 2.