Gala Spins.
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Spin physics Wikipedia.
R, n e i 2 n I cos 2 i n sin 2 displaystyle hat Rtheta hat, mathbf n eifrac theta 2hat mathbf n cdot boldsymbol sigma Icos frac theta 2ilefthat mathbf n cdot boldsymbol sigma rightsin frac theta 2 for higher spins is tractable, but less simple.