The unit circle \(\mathbb{S}^1\subseteq \mathbb{C}\) is together with multiplication a topological group , since it is a subgroup of \((\mathbb{C}\setminus \{0\},\cdot )\) .
The unit circle \(\mathbb{S}^1\subseteq \mathbb{C}\) is together with multiplication a topological group , since it is a subgroup of \((\mathbb{C}\setminus \{0\},\cdot )\) .