Good evening!
Let $ \mathbb{T}:=\{ z \in \mathbb{C} ; \vert z \vert =1 \} $ be the unit circle in the complex plane. We denote the trace Borel-$\sigma$-algebra on $\mathbb{T}$ by $\mathcal{B}(\mathbb{T})$.
Here is my question: Does anyone know an elegant method to construct the Haar-measure (in this case the one-dimensional Lebesgue-measure) on $\mathcal{B}(\mathbb{T})$ ?