Given a real function $f(x_1, \cdots, x_n)$, its level set for $f(x_1, \cdots, x_n) =c$ are the corresponding arguments $x_1, \cdots, x_n$1,

$$L_c(f) = \{ (x_1, \cdots, x_n) \vert f(x_1, \cdots, x_n) =c \}$$

Planted: by ;

L Ma (2022). 'Level Set', Datumorphism, 11 April. Available at: https://datumorphism.leima.is/cards/math/level-set/.