If the length of the latus rectum of a parabola, whose focus is (a, a) and the tangent at its vertex is x+y=a, is 16, then ∣a∣ is equal to :
(A)22
(B)23
(C)42✓ Correct
(D)4
Answer: (C)
Solution
The perpendicular distance from the focus (a,a) to the tangent at the vertex x+y=a is ∣P∣=2∣a+a−a∣=2∣a∣. Since the length of the latus rectum is 4∣P∣, we have 4∣P∣=16, so ∣P∣=4. Therefore 2∣a∣=4, which gives ∣a∣=42.
JEE Main · 2022 · 27 Jul 2022 · Shift 2 · Single correct option