State and prove morera's theorem proving necessary results?

Morera's Theorem states that if a continuous function ( f ) defined on a domain ( D \subseteq \mathbb{C} ) is such that the integral of ( f ) over every closed curve in ( D ) is zero, then ( f ) is holomorphic on ( D ). To prove this, we utilize the fact that if ( f ) is continuous and the integral over every closed curve is zero, we can approximate ( f ) using a partition of unity and apply Cauchy's integral theorem. Thus, by demonstrating that the integral of ( f ) over any disk can be expressed as a limit of integrals over closed curves, we establish that ( f ) is differentiable, confirming that ( f ) is indeed holomorphic.