Show that |
|
|
|
a b
r+b a
r
r
r  is perpendicular to |
|
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a b
r−b a
r
r
r , for any two nonzero
vectors 
aand 
rb
r 12 If 
0  and  
0
a a
a b
⋅
=
⋅
=
r
r r
r
, then what can be concluded about the vector b
r 13