This is LaTeX code:
[latex]
S \times S = \{ (s_{1},s_{2}) \ : \ s_{1},s_{2} \in S \} = \{ (x,y),(u,v)) \ : \ x^{2}+y^{2}=1, \ u^{2}+v^{2}=1 \} \cong \{(x,y,u,v) \ : \ x^{2}+y^{2}=u^{2}+v^{2}=1 \} \subseteq \mathbb{R}^{4}
[/latex]