[center][b]Cauchy Integral Formula[/b][br][/center]Let [math]U[/math] be an open subset of the complex plane [math]\mathbb{C}[/math], and suppose the closed disk [math]D[/math] defined as [br]D={z:|z-w|[math]\le[/math]r} is completely contained in [math]U[/math]. [br]Let [math]f:U\longrightarrow\mathbb{C}[/math] be a holomorphic function, and let [i]C[/i] be the circle, oriented counterclockwise, forming the boundary of [i]D[/i]. [br]Then for every [i]w[/i] in the interior of [i]D[/i], [math]f(w)=\frac{1}{2\pi i}∮_C\frac{f(z)}{z-w}dz[/math].