# Matrix representing a conic

### Description

Build a symmetric matrix representing a quadratic polynomial in two variables.

### Usage

1 | ```
conicMatrix(v)
``` |

### Arguments

`v` |
( |

### Details

The `v`

argument is a 6-length vector containing the
coefficients of a quadratic polynomial of the form:

1 | ```
P(x_1,x_2) = v_1 x_1^2 + v_2 x_1 x_2 + v_3 x_2^2 + v_4 x_1 + v_5 x_2 + v_6
``` |

The associated quadratic form is:

1 | ```
Q(x_1,x_2,x_3) = v_1 x_1^2 + v_2 x_1 x_2 + v_3 x_2^2 + v_4 x_1 x_3 + v_5 x_2 x_3 + v_6 x_3^2
``` |

### Value

Return the symmetric 3x3 matrix representing the associated quadratic form.

### Author(s)

Bernard Desgraupes

bernard.desgraupes@u-paris10.fr

University of Paris Ouest - Nanterre

Lab Modal'X (EA 3454)

### See Also

`conicAsymptotes`

,
`conicAxes`

,
`conicCenter`

,
`conicPlot`

### Examples

1 2 3 | ```
# Equation: 2*x_1^2 + 2*x_1*x_2 + 2*x_2^2 - 20*x_1 - 28*x_2 + 10 = 0
v <- c(2,2,2,-20,-28,10)
conicMatrix(v)
``` |