OA and BO are two vectors of magnitudes 5 and 6 respectively. If BOA = 60°, then OA · OB is equal to
0
15
- 15
A vector perpendicularto the plane containing the points A (1, - 1, 2), B(2, 0, - 1), C(0, 2, 1) is
If k, then the value of k is
9
3
A.
9