Let the latus rectum of the parabola y^2=4x be the common chord to the circles C_1 and C_2 each of them having radius 2√5. Then, the distance between…
JEE Main 2020 — Mathematics Coordinate Geometry
2020mcqhard
Let the latus rectum of the parabola y2=4x be the common chord to the circles C1 and C2 each of them having radius 25. Then, the distance between the centres of the circles C1 and C2 is :
Official previous-year question
Held on 3 Sept 2020 · Verified 6 Jul 2026.
Options
A
12
B
8
C
85
D
45
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Solution
Co-ordinates of focus of parabola will be S=(a,0)=(1,0).
Now, length of latus-rectum =4.
So, length of semi latus-rectum =2.
Also, ∠LSC1=90∘
Now, radius of circle LC1=25
Now, applying pythagoras theorem in △LSC1,
(LC1)2=(C1S)2+(LS)2
⇒(C1S)2=(LC1)2−(LS)2=(25)2−(2)2=16
⇒C1S=16=4
∴C1C2=2C1S=2×4=8.
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