Qayb ka mid ah laamaha S {\displaystyle S} Saddex baaxadood leh R 3 {\displaystyle \mathbb {R} ^{3}} Waa baaxad ee loogu talo galay bar kasta x {\displaystyle x} ka kooban S {\displaystyle S} meelo furan U {\displaystyle U} shaqooyin kala duwan F : U → R {\displaystyle F:U\to \mathbb {R} \,\!} marka U {\displaystyle U} iskajara S {\displaystyle S} bar mucayin ah oo F {\displaystyle F} baaba'da: U ∩ S = F − 1 ( 0 ) {\displaystyle U\cap S=F^{-1}(0)} Meel walba: ∇ F ≠ 0 {\displaystyle \nabla F\neq 0}