Lines and Axes
From GeoGebra Manual
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: 2D
- Type in
g: 3x + 4y = 2
to enter line g as a linear equation. - You can enter a line in parametric form thus:
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.
Example: 3D
- You can enter a line in parametric form thus:
g: X = (1, 6, 3) + λ (7, -4, 4)
; or viag: Line[(1, 6, 3), Vector[(7, -4, 4)]]
- You can enter a line as an intersection of 2 planes, by one of the following 3 equivalent input :
IntersectPath[4x+7y=46,y+z=9]
(4x + 7y = 46, y + z = 9)
7y = 46 - 4x = 7(9 - z)
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 2.2y(a)
the value 3.3z(a)
the value -4.4 (because GeoGebra save the line equation as2.2 x + 3.3 y - 4.4 = 0
.
More informations: Coefficients Command