The Cauchy-Goursat Theorem. Theorem. Suppose U is a simply connected Proof. Let ∆ be a triangular path in U, i.e. a closed polygonal path [z1,z2,z3,z1] with. Stein et al. – Complex Analysis. In the present paper, by an indirect process, I prove that the integral has the principal CAUCHY-GoURSAT theorems correspondilng to the two prilncipal forms.

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Marc Palm 3, 10 Cauchy-Goursat theorem, proof without using vector calculus.

## Cauchy’s integral theorem

If F is a complex antiderivative of fthen. Real number Imaginary number Complex plane Complex conjugate Unit complex number. Instead of a single closed path we can consider a linear combination of closed paths, where the scalars are integers.

Cauchy provided this proof, but it was later proved by Goursat without requiring techniques from vector calculus, or the continuity of partial derivatives. We now state as a corollary an important result that is implied by the deformation of contour theorem.

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The deformation of contour theorem is an extension of the Cauchy-Goursat theorem to a doubly connected prood in the following sense. We can extend Theorem 6. Proof of Theorem 6.

### The Cauchy-Goursat Theorem

One important consequence of the theorem is that path integrals of holomorphic functions on simply connected domains can be computed in a manner familiar from the fundamental theorem of real prolf The Cauchy integral theorem leads to Cauchy’s integral formula and the residue theorem. To be precise, we state the following result.

Let D be a domain that contains and and the region between them, as shown in Figure 6. Is it very complicated? Sign up using Facebook. By using this site, you agree to the Theorwm of Use and Privacy Policy. In other words, there are no “holes” in a simply connected domain. Email Required, but never shown.

Post as a guest Name. If is a simple closed contour that can be “continuously deformed” into another simple closed contour without passing through a point where f is not analytic, then the value of the contour integral of f over is the same as the value of the integral of f over.

This version is crucial for rigorous derivation of Laurent series and Cauchy’s residue formula without involving any physical notions such as cross cuts or deformations.

If C is positively oriented, then -C is negatively oriented. If C is a simple closed contour that lies in Dthen.

The Cauchy-Goursat theorem states that within certain domains the integral of an analytic function over a simple closed contour is zero. Hence C is a positive orientation of the boundary of Rand Theorem 6. Return to the Complex Analysis Project. This page was last edited on 30 Aprilat You may want to compare theore, proof of Corollary 6.

### Cauchy’s integral theorem – Wikipedia

This result occurs several times in the theory to be developed and is an important tool for computations. Recall also that a domain D is a connected open set. Sign up using Priof and Password. Briefly, the path integral along a Jordan curve of a function holomorphic in the interior of the curve, is zero. Not to be confused with Cauchy’s integral formula. We want to be able to poof integrals over certain complicated contours with integrals that are easy to evaluate.

The Cauchy integral theorem is valid in slightly stronger forms than given above. The theorem is usually formulated for closed paths as follows: Spine Feast 1, 1 23