🌐EnglishEnglish中文日本語EntityQ3303275· pop 5· linked from 9 articlesBeltrami identityspecial case of the Euler-Lagrange equationAvailable in 5 languages中文AlbanianCatalanDanishvia Wikidata sitelinks · CC0Connectionslist of differentiation rulesEntitydifferentialEntityCategoriesCalculus of variationsOptimal control