Passage
Let be the origin, and be three unit vectors in the directions of the sides , respectively, of a triangle .Let be the origin, and be three unit vectors in the directions of the sides , respectively, of a triangle .
- (A)✓ Correct
- (B)
- (C)
- (D)
Answer: (A)
Solution
The vectors and are unit vectors in the directions of sides and respectively.
The angle between and is (exterior angle at ).
Therefore:
Since , we have , so:

The angle between and is (exterior angle at ).
Therefore:
Since , we have , so:

JEE Advanced · 2017 · 21 May 2017 · Paper 2 · Single correct option