2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/170042A simple proof is given of the following result first observed by J. Adachi: embedded circles tangent to the standard Engel structure on Euclidean 4-space are classified, up to isotopy via such embeddings, by their rotation number.4 pagesGeometric TopologySymplectic Geometry57R40; 57R42, 57R15, 53D10text