# Definition:Contour/Image/Complex Plane

## Definition

Let $C$ be a contour in $\C$ defined by the (finite) sequence $\sequence {C_1, \ldots, C_n}$ of directed smooth curves in $\C$.

Let $C_k$ be parameterized by the smooth path $\gamma_k: \closedint {a_k} {b_k} \to \C$ for all $k \in \set {1, \ldots, n}$.

The image of $C$ is defined as:

$\ds \Img C := \bigcup_{k \mathop = 1}^n \Img {\gamma_k}$

where $\Img {\gamma_k}$ denotes the image of $\gamma_k$.

If $\Img C \subseteq D$, where $D$ is a subset of $\C$, we say that $C$ is a contour in $D$.