u got that modulus of p vector....dont u?

 

p , b , a are mutually perpendicular.

 

by definition of cross product, in ( b x a) the resultant will be perpendicular both to  b and a.............the direction of p vector is also perpendicular both to b and a.

 

hence, p vector and ( b x a) are in the same direction.

 

magnitude of p vector is already found.

 

to show direction a unit vector in the direction of ( b x a) is taken.........i.e

 

( b x a )

---------------

| b x a |