Integrals#
Definition: Integral of a Real Vector Function
Let \(f: \mathcal{D} \subseteq \mathbb{R}^m \to \mathbb{R}^n\) be a real vector function with component functions \(f_1,\dotsc,f_n\) and let \(S \subseteq \mathbb{R}^m\).
We say that \(f\) is integrable on \(S\) if \(f_1,\dotsc,f_n\) are integrable on \(S\). In this case, we define the integral of \(f\) over \(S\) as the real vector
\[ \int_S f(\mathbf{x}) \mathop{\mathrm{d}^m\mathbf{x}} \overset{\text{def}}{=} \begin{bmatrix}\int_S f_1(\mathbf{x}) \mathop{\mathrm{d}^m\mathbf{x}} \\ \vdots \\ \int_S f_n(\mathbf{x}) \mathop{\mathrm{d}^m\mathbf{x}} \\ \end{bmatrix} \]