The binary tetrahedral group is most easily described concretely as a discrete subgroup of the unit quaternions, under the isomorphism \ operatorname { Spin } ( 3 ) \ cong \ operatorname { Sp } ( 1 ) where Sp ( 1 ) is the multiplicative group of unit quaternions . ( For a description of this homomorphism see the article on quaternions and spatial rotations .)
32.
The binary octahedral group is most easily described concretely as a discrete subgroup of the unit quaternions, under the isomorphism \ operatorname { Spin } ( 3 ) \ cong \ operatorname { Sp } ( 1 ) where Sp ( 1 ) is the multiplicative group of unit quaternions . ( For a description of this homomorphism see the article on quaternions and spatial rotations .)
33.
:Leon's answer is the one you're looking for, but for what it's worth, you can represent a 4D rotation with a pair of unit quaternions ( six degrees of freedom in total ), as described in Quaternions and spatial rotation # Pairs of unit quaternions as rotations in 4D space ( read the rest of the article too ).
34.
As a subgroup of the spin group, the binary cyclic group can be described concretely as a discrete subgroup of the unit quaternions, under the isomorphism \ operatorname { Spin } ( 3 ) \ cong \ operatorname { Sp } ( 1 ) where Sp ( 1 ) is the multiplicative group of unit quaternions . ( For a description of this homomorphism see the article on quaternions and spatial rotations .)
