# Problem with Inequations! Bug or not?

Birgit Lachner shared this question 9 years ago

I thought it it was possible to intersect the lines of inequations at the beginning?

Now, even simple inequations like x<=1 and y<=2 could not be intersected. I tried it with an example of three inequations and luckily get one intersection ... see picture (need to add it, because I'm under Windows and the picture is on Linux) ... but the Intersect-Command has one starting-point. This is a bit confusing as this option does not appear when typing the command "Intersect" ("Schneide" in german?).

And this command is not useable, when trying to enter the definition once again I got an error ... see picture.

I do understand that the intersection of two inequations is not only one point. And there is of cause a solution/workaround by drawing the corresponding equations.

A collegue wanted to get the intersection-points of inequations to draw a polygon for the area that is described by all the inequations, to have a point inside this polygon.

Is there a better way to get this polygon?

Birgit 1

Try the new Vertex command in GeoGebra 4.2, eg

Vertex[(x + y < 3) && (x - y > 1)]

(wiki still needs update :) ) 1

Nice ... but should the description not be:

Vertex[ <Inequalites> ]

... or something else because it dos not work with one inequality or even with y>x^2

One simple to use solution might be to make a common tool that uses the Vertex-Command. Take the tool and click on both inequalities.

Birgit 1

I added those informations in the german wiki pages:

- Inequation

- Vertex

- Intersect