Q.

Let A, B, C be three points in xy-plane, whose position vector are given by 3i^+j^, i^+3j^ and ai^+(1–a)j^ respectively with respect to the origin O. If the distance of the point C from the line bisecting the angle between the vectors OA→ and OB→ is 92, then the sum of all the possible values of a is :          [2025]

1 1  
2 0  
3 9/2  
4 2  

Ans.

(1)

Equation of line OA is x–3y=0

Equation of line OB is 3x–y=0

Equation of angle bisector is x–3y1+3+3x–y3+1=0

⇒ x–y=0

|a–(1–a)2|=92 ⇒ a=5 or –4

Required sum = 5 + (–4) = 1.