If the line segment joining the points (5,2) and (2,a) subtends an angle 4π at the origin, then the absolute value of the product of all possible values of a is :
(A)6
(B)8
(C)2
(D)4✓ Correct
Answer: (D)
Solution
Slopes from origin: mOA=2/5, mOB=a/2. Angle between them is π/4:
tan4π=1+(a/2)(2/5)a/2−2/5=1⟹10+2a5a−4=1
5a−4=±(10+2a)
5a−4=10+2a⟹a=14/3; \quad 5a−4=−10−2a⟹a=−6/7. Product of possible values: 314×(−76)=−4, absolute value =4.
JEE Main · 2024 · 08 Apr 2024 · Shift 2 · Single correct option