CORK SCREW RULE: The vector C  is normal to the plane of A and B   are points in the direction in which a right handed screw would advance when rotated about an axis perpen- dicular to the plane of the two vectors in the direction from A to B   through the smaller angle  between them or, alternatively, we might state the rule as: If the fingers of the right hand be curled in the direction in which vector A  must be turned through the smaller included angle  to coincide with the direction of vector B  , the thumb points in the direction of C  as shown in figure. Either of these rules is referred to as the right handed screw rule. Thus, if nˆ be the unit vector in the direction of C  , we have C A B ABsin n    ˆ    where 0     .

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