8 (ii)), we have
AB
BC
+
uuur
uuur  = AC
uuur
Now again, since AC
CA
= −
uuur
uuur
, from the above equation, we have
AB
BC
CA
+
+
uuur
uuur
uuur
 = AA
0
=
uuur
r
This means that when the sides of a triangle are taken in order, it leads to zero
resultant as the initial and terminal points get coincided (Fig 10 8(iii)) Fig 10 7
a
b
a
b
(i)
(iii)
A
C
a
b
(ii)
a
b
+
A
C
B
B
a
b
–
–b
C’
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 MATHEMATICS
430
Now, construct a vector BC′
uuuur
 so that its magnitude is same as the vector BC
uuur
, but
the direction opposite to that of it (Fig 10