context | $\langle X,\Sigma,\mu\rangle\in \mathrm{MeasureSpace}(X)$ |
postulate | $\int_X:\mathcal T^+\to \mathbb R_+$ |
$ f\equiv \sum_{j=1}^n\alpha_j\cdot\chi_{E_n} \in \mathcal T^+$ |
postulate | $\int_X\ f\ \mathrm d\mu:=\sum_{j=1}^n\alpha_j\cdot\mu(E_n) $ |