# The Cartesian equation of a geometric object in the plane: equation

### 13.13.7 The Cartesian equation of a geometric object in the plane: equation

See Section 14.12.5 for Cartesian equations of three-dimensional objects.

The equation command finds the Cartesian equation for a geometric object.

- equation takes one argument:
  G, a geometric object.
- equation(G) returns the Cartesian equation in the variables x and y for G.

Note that x and y must be formal variables, you might need to purge them with with purge(x) and purge(y), see Section 4.4.8.

#### Example.

Input:

equation(line(-1,i))

Output:

y=x+1