# Create 2d from arbitrary eq

Dave Yrueta shared this question 5 months ago

HI All --

While I understand the basics (right click on a surface, select the command, type a 2d function / expression into the expression bar), I'd like to know more. Are there any docs that explain how this command works. In particular, I'm interested in knowing under what contexts Geogebra interprets an expression in either 2d or 3d.

For example, if I define the plane eq1: 2x + 3y + 4z = 1, right click on the surface, select "Create 2d from eq1", then type 2x + 3y = 0 in the field below it, it will produce a the line 2x + 3y = 0 in the xy plane, but no line is visible in split-screen that is produced after selecting the command.

If I continue to write expressions of the form ax+by = c, it produces the 2d versions of those line. However, certain combinations of mouse clicks force those expressions to be irreversibly interpreted in a 3d context.

Any help on how to use this very neat but somewhat confusing command would be greatly appreciated!

1

It will depend if the 3D or 2D views have the focus when you type the expression

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How do I bring the level curve into view in the 2D panel? For example, if I type 2x+3y+4z = 1, select "2D view from eq1", and then type 2x + 3y = 0, a line displays in the 3D view, but no line appears in the split screen. Also, why are there no grid lines in 2D panel?

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Thank you!