= Solution
The <Cauchy integral formula> says that if $f$ is <holomorphic> on the <simply connected> <open set> $U$, and $\gamma$ is a positively oriented <simple closed curve> in $U$, then, for every $z$ in its interior,
$$
\boxed{f(z)=\frac1{2\pi i}\int_\gamma\frac{f(\zeta)}{\zeta-z}\,d\zeta.}
$$
Here the contour and its enclosed region lie in $U$; the contour can be taken piecewise continuously differentiable. More generally, the same formula needs only <holomorphic function> on an <open neighbourhood> of that closed region. The orientation is counterclockwise, so the <winding number> about an interior point is one.
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