Given that 
 What can you conclude about the vectors 
?
Given that
![]()
 (where θ is the angle between the vectors)
![]()
Also given that,
![]()
 (where θ is the angle between the vectors)
![]()
As there is no value of θ for which both sin θ and cos θ are zero.
Therefore, the condition for which 
 and 
 is:
.