Introduction

Feynman Integral is a powerful integration technique as we use the method of differentiating under the integral sign. Feynman's Technique of integration utilizes parametrization and a mix of other different mathematical properties in order to integrate an integral that is can't be integrated through normal processes like u-substitution or integration by parts. It primarily focuses on setting a function equal to an integral and then differentiating the function to get an integral that is easier to work with. This technique is also popularly known as the "Leibniz Integral Rule".

Richard Philip Feynman, an American theoretical physicist, is known for this integration technique along with his other works in the theory of quantum electrodynamics, path integral formulation of quantum mechanics, the physics of the superfluidity of supercooled liquid helium, and in particle physics for which he proposed the parton model.