What is the best software if I want to plot an interval, say $[0,+\infty) \times[5,10]\subset\mathbb{R}^2$? Preferably freely available. Of course I could do this with Desmos, LaTeX, or even Excel – but all of them seem quite inconvenient. I know Mathematica is probably the best but unfortunately I don't have access to it.
Best software/website to plot intervals
graphing-functionsinterval-arithmeticmath-software
Related Solutions
Have you tried this online MMA Web Based tool to do a 3D Plot of Vector Fields?
You might also try have a look here and see if any of the free SW listed works for you (GNU Plot, JavaView, Visual Data...).
Have fun!
Regards
Although this is a late answer neverthless it may be useful for some other readers.
I would recommend Geogebra which is a dynamic mathematics software for learning and teaching mathematics. It is also open source software.
3D properties have been added to geogebra version 5. You can easily create 3D objects like pyramids, prisms, spheres, cylinders, cones ... or you can draw graphics of multivariable functions of the form $f(x,y)$ simply.
For example from View->3D Graphics
in command line, type $f(x,y)=x^2+y^2$
or type $y=-5 $ for plane graph
You can explore the rich properties of Geogebra in time.
Best Answer
I will recommend GeoGebra Classic, it is FREE and joins graphing, geometry, 3D, spreadsheets, computer algebra and probability in one easy-to-use and powerful package.
Figure. In input field type this: $x >= 0 \quad \&\& \quad 5 <= y <= 10$