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by tagrun 966 days ago
Quaternions that represent 3D rotations have exactly 3 parameters, because they are normalized: https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotati...

Quaternions that are not normalized do not form a representation of the spin group Spin(3).
1 comments
Hydraulix989 966 days ago
I'm assuming Spin(3) is equivalent to SO(3)?
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tagrun 966 days ago
It's a double cover of SO(3) (because q and -q correspond to the same element of SO(3)), and is isomorphic to SU(2)
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Hydraulix989 966 days ago
Oh wow thanks I understand
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