i e a b
⋅
rr
= b a
⋅
r r           (Why )
Two important properties of scalar product
Property 1 (Distributivity of scalar product over addition) Let ,   and  
a b
c
rr
r  be
any three vectors, then
(
)
a
b
c
⋅
r+
r
r  =
 
 
a b
a c
⋅
+
⋅
rr
r r
Fig 10