Let a circle C pass through the points (4,2) and (0,2), and its centre lie on 3x+2y+2=0. Then the length of the chord, of the circle C , whose midpoint is (1,2), is:
(A)3
(B)23✓ Correct
(C)42
(D)22
Answer: (B)
Solution
A(4,2) and B(0,2) have the same y-coordinate, so the perpendicular bisector of AB is the vertical line x=2. Combined with the centre condition 3x+2y+2=0:
3(2)+2y+2=0⇒y=−4
so the centre is O=(2,−4), and r2=OA2=(2−4)2+(−4−2)2=4+36=40.
The chord's midpoint is N=(1,2), and ON2=(2−1)2+(−4−2)2=1+36=37.
chord length=2r2−ON2=240−37=23
JEE Main · 2025 · 29 Jan 2025 · Shift 2 · Single correct option