# Difference between revisions of "Lines and Axes"

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## 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.

## Get parameters of a line

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

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