Hy, I need to calculate angle from 2x2 rotation matrix. How exactly i can do that?

Thank you, for help.

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- Sep 27th 2010, 03:05 PMPJaniAngle from 2x2 rotation matrix
Hy, I need to calculate angle from 2x2 rotation matrix. How exactly i can do that?

Thank you, for help. - Sep 27th 2010, 03:25 PMundefined
You mean this kind of rotation matrix?

$\displaystyle \begin{bmatrix} \cos \theta & -\sin \theta \\ \sin \theta & \cos \theta \\ \end{bmatrix}$

Rotation matrix - Wikipedia, the free encyclopedia

You can derive the rotation matrix by considering what (1,0) and (0,1) map to when rotated by angle theta.

If you have a matrix of that form and need to find theta, you can do so using inverse trig functions. - Sep 27th 2010, 03:38 PMPJani
Jep this form i mean.

This will look weird but i just want to get sure its correct.

$\displaystyle \begin{bmatrix} acos(\cos \theta) & asin(--\sin \theta) \\ asin(\sin \theta) & acos(\cos \theta) \\ \end{bmatrix}$

and all elements must be the same if i am not mistaking. - Sep 27th 2010, 03:56 PMundefined
- Sep 27th 2010, 04:19 PMPJani
It is part of my answer.

hmm full question...

...Actually i am working on 2D game. And for debug display its hard to read 2x2 transformation matrix in realtime. So i only want to get angle and display it. - Sep 27th 2010, 06:22 PMundefined