Geometric harmonic analysis ; 1: A sharp divergence theorem with nontangential pointwise traces This monograph presents a comprehensive self contained and novel approach to the Divergence Theorem through five progressive volumes. Its ultimate aim is to develop tools in Real and Harmonic Analysis of geometric measure theoretic flavor capable of treating a broad spectrum of boundary value problems formulated in rather general geometric and analytic settings. The text is intended for researchers graduate students and industry professionals interested in applications of harmonic analysis and geometric measure theory to complex analysis scattering and partial differential equations. Volume I establishes a sharp version of the Divergence Theorem (aka Fundamental Theorem of Calculus) which allows for an inclusive class of vector fields whose boundary trace is only assumed to exist in a nontangential pointwise sense.