© NCERT
not to be republished
VECTOR ALGEBRA
455
10 Find the area of the parallelogram whose adjacent sides are determined by the
vectors 
ˆ
ˆ
ˆ
3
a
i
j
k
=
−
+
r
and 
ˆ
ˆ
ˆ
2
7
b
i
j
k
=
−
+
r 11 Let the vectors 
a  and  
rb
r
 be such that 
2
|
| 3  and |
|
3
a
b
=
r=
r
, then a
×b
r
r
 is a
unit vector, if the angle between   and  
a
rb
r
 is
(A) π/6
(B) π/4
(C) π/3
(D) π/2
12