# Difference between revisions of "Lines and Axes"

From GeoGebra Manual

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* Define the parameters m = 2 and b = -1. Then, you can enter the equation<br><code>h: y = m*x + b</code> to get a line h in y-intercept-form.}} | * Define the parameters m = 2 and b = -1. Then, you can enter the equation<br><code>h: y = m*x + b</code> to get a line h in y-intercept-form.}} | ||

==Axes== | ==Axes== | ||

− | The two coordinate axes are available in commands using the names xAxis and yAxis. | + | The two coordinate axes are available in commands using the names ''xAxis'' and ''yAxis''. |

{{example|1=The command <code>[[PerpendicularLine Command|PerpendicularLine]][A, xAxis]</code> constructs the perpendicular line to the x-axis through a given point A. }} | {{example|1=The command <code>[[PerpendicularLine Command|PerpendicularLine]][A, xAxis]</code> constructs the perpendicular line to the x-axis through a given point A. }} |

## Revision as of 10:20, 26 July 2011

## Lines

You can enter a line as a linear equation in x and y or in parametric form into the Input Bar. In both cases previously defined variables (e. g. numbers, points, vectors) can be used within the equation.

**Note:**You can enter a line’s name at the beginning of the input followed by a colon.

**Example:**

- Type in
`g: 3x + 4y = 2`

to enter line g as a linear equation. - Define a parameter t (e. g., t = 3) before entering line g in parametric form using
`g: X = (-5, 5) + t (4, -3)`

. - Define the parameters m = 2 and b = -1. Then, you can enter the equation
`h: y = m*x + b`

to get a line h in y-intercept-form.

## Axes

The two coordinate axes are available in commands using the names *xAxis* and *yAxis*.

**Example:**The command

`PerpendicularLine[A, xAxis]`

constructs the perpendicular line to the x-axis through a given point A.## Comments

## Get parameters of a line[edit]

From the line `a: 2.2 x + 3.3 y = 4.4`

you'll get with

`x(a)`

the value 2.2`y(a)`

the value 3.3`z(a)`

the value -4.4 (because GeoGebra save the line equation as`2.2 x + 3.3 y - 4.4 = 0`

.

More informations: Coefficients Command