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Page history last edited by Mike May, S.J. 11 years, 4 months ago

Graphing Inequalities with GeoGebra 4.0


Verified with 3.9.283


One of the new features of GeoGebra with release 4.0 is the ability to graph inequalities. You simply enter the inequality in the input bar. We start with the linear inequality x+y<5.


Besides linear inequalities, you can also do inequalities with conics. Following standard notational conventions, solid boundaries are used to indicate that the boundary is included, while dashed boundaries indicate that the boundary is not included.


You can also graph inequalities involving other functions as long as the relation is linear in one of the two variables.


We often want to look at systems of inequalities. A simple case is when we want to look a region subject to three linear inequalities.


In order to make the picture clearer, we go to the object properties for the inequalities and change the fill so that at least some of the inequalities are indicated by different kinds of hatching.


Even with the hatching, it can be difficult to see the intersection of the inequalities. It is thus useful to add a combined inequality to show the intersection.


We can then hide the original inequalities and show the intersection.


When writing combined inequalities, you can use && to represent "and" while using || to represent "or". You can also use the "and" and "or" symbols from the symbol palette in the input bar.


It is worth noting that an inequality is a special case of a Boolean function. For each of the points A and B, I can create a test function to see if the point satisfies the inequality. Thus we can define dTestA = d(x(A),y(A)).


Notes on details that are still fluid.

It seems that inequalities cannot have labels.

The visual redefinition of an inequality is not currently working.

The not symbol can be used.


Except where otherwise noted, content on this site is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 license, Mike May, S.J. maymk@slu.edu


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