The latest 2023 version now does a calculation with the path for divergence as flux/vol and curl as circulation/area (the other moveable div and curl meters used the symbolic formulas).[br][br][i]You can modify the various paths. In some cases, you may be able to rigidly move the path by grabbing the faint grey line joining two control points.[/i][br][br]The original 2019-version is based on [url=https://www.geogebra.org/m/XfmAAUTG]https://www.geogebra.org/m/XfmAAUTG[/url][br](Vector Fields, Divergence, Curl, and Line Integrals  by  Erik Jacobsen)[br]which is claimed to be [br]based on (presumably) [url=https://www.geogebra.org/m/UstetaTp]https://www.geogebra.org/m/UstetaTp[/url][br](Vector Fields and Line Integrals by George Sturr).[br][br]The "Purcell" vector fields are based on E.M. Purcell's Electricity and Magnetism textbook.[br]