# Definition:Contour Integral/Complex/Closed

## Definition

Let $C$ be a closed contour in $\C$.

Then the symbol $\ds \oint$ is used for the contour integral on $C$.

The definition remains the same:

$\ds \oint_C \map f z \rd z := \sum_{k \mathop = 1}^n \int_{a_k}^{b_k} \map f {\map {\gamma_k} t} \map {\gamma_k'} t \rd t$