Set of points of coordinates $\left(x,y\right)$ so that $f\left(x,y\right)=0$.

- Shortcut: Ctrl+I
- We give a name.
- we give a command like f(x,y), or [f(x,y),n,m], n stands for the subdivisions number of the Ox axe and m the subdivisions number of the Oy axe (50 by default). On each pavement obtained, a sign change is tested, if yes then a dichotomy is applied on the edges of the pavement.
- Corresponding graphical command: Implicit (to be used in a User-defined type element).