If a vector 
is perpendicular to two non-collinear vectors 
and 
then 
is perpendicular to every vector in the plane of 
and 
.
Given 
is perpendicular to 
and 
,so 
and 
Let a random vector 
in the plane of 
where p and k are some arbitrary constant
Taking dot product of 
Using 
and 
Hence, proved………
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