If 
and 
then write the value of 
Given
and
We know the dot product of two vectors 
and 
forming an angle θ is
We also know the cross product of two vectors 
and 
forming an angle θ is
where 
is a unit vector perpendicular to
and 
is a unit vector 
We have
But, we know sin2θ + cos2θ = 1
Thus,
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