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# 10 20-12-2010 , 07:15 AM
Chirone's Avatar
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Join Date: Dec 2007
Location: NZ
Posts: 3,125

Is 2a something along the line like this
R =
cos(45degrees) -sin(45degrees)
sin (45degrees) cos(45degrees)

that's a rotation matrix.
but you see how it's only a 2x2 matrix? (pronounced 2 by 2)
that means it only applies in 2D space because it can only be multiplied by 2 dimensional vectors (vectors with 2 components in them such as (2,3))
the second sentence in this link: https://en.wikipedia.org/wiki/Rotation_matrix explains so

3D has x, y, and z.
see if you can find the rotation matrix for that.
actually, there are a few, one that rotates around x, one that rotates around y, and one that rotates around z, and one that is all of them at once.

wait, i just re-read your second question in your second post. yeah, the 2d rotation matrix is the one you want..




that's a "Ch" pronounced as a "K"

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Last edited by Chirone; 20-12-2010 at 11:09 AM.