The parabola in the plane: parabola

### 13.12.3 The parabola in the plane: parabola

See Section 14.11.3 for parabolas in space.

The parabola command draws parabolas and other conic sections. parabola can take parameters in different forms.

- - parabola can take one argument:
    eqn, a second degree equation in the variables x and y (or an expression which will be set to zero).
  - parabola(eqn) returns and draws the conic section given by the equation eqn.

  #### Example.

  Input:

  parabola(x^2 - y - 1)

  Output:

- - parabola can take two arguments:
    F,V, two points.
  - parabola(F,V) returns and draws the parabola with focus F and vertex V.

  #### Example.

  Input:

  parabola(0,i)

  Output:

- - parabola can take two parameters:
    - A=(a,b), a point.
    - c, a real number.
  - parabola(A,c) returns and draws the parabola y = b + c(x − a)2.

  #### Examples.

  - Input:
    parabola(-i,1)
    Output:
  - Input:
    parabola(-i,i,1/2)
    Output: