By: Mr. Smith

Mr. Smith — Fri, 19 Feb 2010 04:39:59 +0000

It is a bit different, though the same basic concept. Let’s say you have two coordinates, (A, B, C) and (X, Y, Z). Your cross product will be

(BZ – CY, XC – ZA, AY – BX).

Give me a second to type how to remember it:

First, position the coordinates above each other visually, with the first one on top (yes, order does matter):

(A, B, C)
(X, Y, Z)

For the first term, cover up the first values:

( , B, C)
( , Y, Z)

and then multiply the B times Z, subtracting from that C times Y (BZ – CY).

For the second term, cover the middle values:

(A, , C)
(X, , Z)

And multiply and subtract again, but this time switch directions. Start with the first value in the second coordinate (XC – ZA)

For the third term, cover the last values:

(A, B, )
(X, Y, )

and then multiply and subtract, starting with the value in the first coordinate again (AY – BX).
References :

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