Using the axiom of choice, we pick a single point from each orbit and call this set <math>W \ </math>. Note that <math>\mathbb{F}(W) = \mathbb{S}^2 - B \ </math>. | Using the axiom of choice, we pick a single point from each orbit and call this set <math>W \ </math>. Note that <math>\mathbb{F}(W) = \mathbb{S}^2 - B \ </math>. |