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# Matrix quick question watch

1. "Write down the 2 × 2 matrix which represents a rotation about (0, 0) through –90°."

I get :

0---1
1---0

0--1
-1-0

Whose right? This is frustrating me. And also, then you have a transformation, do you put the object to transform before or after the actual transformation during multiplication?

Thanks!
2. The rotation matrix is [{cos x, -sin x}, {sin x, cos x}] = [{0,-(-1)},{-1,0}] = [{0,1},{-1,0}] when evaluated at x = -90.
3. Check that you're rotating it the right way (ie. Clockwise or Anti-clockwise)
4. yes i think ur right
and u should put the transformation matrix before the object
peace
5. (Original post by musicbaserich)
Check that you're rotating it the right way (ie. Clockwise or Anti-clockwise)
Oh I see. So is -90 clockwise? I was rotating it anti.

So i guess I'm wrong. Thanks

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