| The following theorem shows that the values of an analytic function interior to a simple closed contour are completely determined by the values of on .
Cauchy's Integral Formula: Let be analytic in the simply connected domain , and let be a simple positively oriented contour that lies in . If is a point that lies interior to , then 
Example: Find .
Let . Observe that is analytic on and inside .
By applying Cauchy's integral formula, we get Therefore, |