Ellipse in the plane

### 26.11.1 Ellipse in the plane

For ellipses in space, see Section 27.9.2.

The ellipse command draws ellipses and other conic sections. ellipse can take parameters in two different ways.

- ellipse can take one argument: eqn, a second degree equation in the variables x and y (or an expression which will be set to zero).
- ellipse(eqn) returns and draws the conic section given by eqn.
- Alternatively, ellipse can take three arguments:
  - A,B, two points.
  - C, a point or a real number.
- ellipse(A,B,C) returns and draws the ellipse with foci A and B and passing through C (if C is a point) or whose semi-major axis has length C (if C is a real number).
- Note that if the third argument is a point on the real axis, the real affix of the point won’t work, it needs to be specified with the point command.

#### Examples

ellipse(x^2+2*y^2-1)

ellipse(-i,i,i+1)

ellipse(-i,i,sqrt(5)-1)