Fundamental Theorem of Contour Integration

Theorem
Let $D \subseteq \C$ be an open set.

Let $f: D \to \C$ be a continuous function.

Suppose that $F: D \to \C$ is an antiderivative of $f$.

Let $\gamma: \closedint a b \to D$ be a contour in $D$.

Then the contour integral:
 * $\ds \int_\gamma \map f z \rd z = \map F {\map \gamma b} - \map F {\map \gamma a}$

Proof
By the chain rule:
 * $\dfrac \d {\d t} \map F {\map \gamma t} = \map {F'} {\map \gamma t} \map {\gamma'} t = \map f {\map \gamma t} \map {\gamma'} t$

Thus: