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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not to be republished
 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 8 (iii)), i e ,
BC′
uuuur
 =
BC
−
uuur
Then, on applying triangle law from the Fig 10