The Cauchy integral theorem says the integral around a closed curve is zero for an analytic function. 柯西积分定理说:对解析(全纯)函数而言,沿闭合曲线的积分为零。
Using the Cauchy integral theorem, we can show that the value of a contour integral depends only on the endpoints when the function is holomorphic on a simply connected region. 利用柯西积分定理,我们可以证明:当函数在单连通区域内全纯时,沿路径的复积分只与端点有关,而与具体路径无关。