Let , and . If the vector lies in the plane of and , then equals
- (A)0
- (B)1
- (C)-4
- (D)-2✓ Correct
Answer: (D)
Solution
The vector lies in the plane of and exactly when the three are coplanar, so their scalar triple product vanishes: . Expanding gives , that is . Hence .
JEE Main · 2007 · 29 Apr 2007 · Offline · Single correct option