The vector product in coordinates. Consider vectors
and .
Let us find the coordinate of their vector product. Property 4 allows us to multiply them term by term
.
Since the vector products of collinear vectors equal zero, it follows that the first, fifth and ninth terms are null vectors:
Consider the vector products of the unit mutually perpendicular vectors and . Since, , and is a right triple of vectors, it follows from the definition of vector product and its commutativity that
; ; ; ; ; . (*)
Substituting the products of unit vectors into the required vector product, we obtain
Note that the right – hand side is the expansion of a third – order determinant along the row with elements and .
Thus, the coordinates of the vector product are determined form the third – order determinant as
,
and its absolute value is
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