Consider a triangle having vertices A(-2,3),B(1,9) and C(3,8). If a line L passing through the circum-centre of triangle ABC, bisects line BC, and…
JEE Main 2021 — Mathematics Coordinate Geometry
2021integereasy
Consider a triangle having vertices A(−2,3),B(1,9) and C(3,8). If a line L passing through the circum-centre of triangle ABC, bisects line BC, and intersects y-axis at point (0,2α), then the value of real number α is _______.
Official previous-year question
Held on 20 Jul 2021 · Verified 6 Jul 2026.
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Solution
We have,
AB=(−2−1)2+(3−9)2=45
AC=(−2−3)2+(3−8)2=50
BC=(3−1)2+(8−9)2=5
Here,
AC2=AB2+BC2
⇒(50)2=(45)2+(5)2
Hence, ∠B=90∘, so circumcentre is the mid-point of hypotenuse i.e., AC.
Circumcenter ≡(21,211)
Mid-point of BC=(2,217)
Equation of line L is
(y−211)=(21−2211−217)(x−21)
⇒y=2x+29
Passing though (0,2α), so
2α=29⇒α=9
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