2D implicit curve

### 18.6.1 2D implicit curve

- For an implicit plot in ℝ2, plotimplicit takes three mandatory arguments and three optional arguments:
  - expr, an expression of two variables implicitly defining a curve by expr=0.
  - vars, a list of the two variables, optionally with their ranges var=a..b. If a range is not given, the ranges are determined by WX-, WX+ and WY-, WY+ in the graphical configuration (see Section 2.5.8).
  - Optionally, xstep, which can be xstep=n to specify the discretization step in the x direction.
  - Optionally, ystep, which can be ystep=m to specify the discretization step in the y direction.
  - Optionally, unfactored.
- plotimplicit(expr,vars ⟨,xstep,ystep,unfactored ⟩) draws the graphic representation of the curve defined by the implicit equation expr=0 over the given ranges of the variables.

#### Example

plotimplicit(x^2+y^2-1,x,y)

or:

plotimplicit(x^2+y^2-1,x,y,unfactored)