3 If a unit vector ar  makes angles 
ˆ
ˆ
with ,
with
3
i4
j
π
π
 and an acute angle θ with
ˆk , then find θ and hence, the components of ar 4 Show that
(
)
(
)
a
b
a
b
−
×
+
r
r
r
r
 = 2(
a b)
×
r
r
5