Definition:Primitive (Calculus)/Vector-Valued Function

Definition
Let $U \subset \R$ be an open set in $\R$.

Let $\mathbf f: U \to \R^n$ be a vector-valued function on $U$:


 * $\forall x \in U: \mathbf f \left({x}\right) = \displaystyle \sum_{k \mathop = 1}^n f_k \left({x}\right) \mathbf e_k$

where:
 * $f_1, f_2, \ldots, f_n$ are real functions from $U$ to $\R$
 * $\left({e_1, e_2, \ldots, e_k}\right)$ denotes the standard ordered basis on $\R^n$.

Let $\mathbf f$ be differentiable on $U$.

Let $\mathbf g \left({x}\right) := \dfrac \rd {\rd x} \mathbf f \left({x}\right)$ be the derivative of $\mathbf f$ $x$.

The primitive of $\mathbf g$ $x$ is defined as:


 * $\displaystyle \int \mathbf g \left({x}\right) \rd x := \mathbf f \left({x}\right) + \mathbf c$

where $\mathbf c$ is an arbitrary constant vector.