Thus, we may say that the two laws of vector
addition are equivalent to each other Properties of vector addition
Property 1 For any two vectors 
aand
rb
r
,
a
b
+
r
r
 = b
a
+
r
r
(Commutative property)
Fig 10 9
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not to be republished
VECTOR ALGEBRA
431
Proof Consider the parallelogram ABCD
(Fig 10 10)