�Note   In Example 21, one may note that although AB
BC
CA
0
+
+
=
uuur
uuur
uuur
r  but the
points A, B and C do not form the vertices of a triangle EXERCISE 10 3
1 Find the angle between two vectors 
aand 
rb
r
with magnitudes 
3  and 2 ,
respectively having 
6
a b
⋅
=
rr