Message Boards Message Boards

0
|
2915 Views
|
2 Replies
|
1 Total Likes
View groups...
Share
Share this post:

How can I find the boundary function in RegionPlot?

Posted 10 years ago

Hello

I have a problem with finding the function that gives the boundary curve in RegionPlot command. I use the following code to make the regions

RegionPlot[{{x^3 - y^2 > 2 y && x^2 + y^3 > 2 x }, {x^3 - y^2 < 2 y && x^2 + y^3 > 2 x }}, {x, -1, 1}, {y, -1, .1}, PlotStyle -> {Green, Yellow}, BoundaryStyle -> {Black, Thick}]

Here we see a black thick curve between the green and yellow regions, I mean the boundary that separates the black and green regions (I showed it with a red arrow).

Now, how can I find its equation or at least the list of points living on this curve?

Best Hadi

Attachments:
POSTED BY: Amir Hadi Ziaie
2 Replies

Both regions have x^2 + y^3 > 2 x but the first has x^3 - y^2 > 2 y and the second has x^3 - y^2 < 2 y, so I would expect the boundary to be x^2 + y^3 == 2 x where x^2 + y^3 > 2 x. You can check this with

ContourPlot[x^3 - y^2 == 2 y, {x, -1, 1}, {y, -1, 1}, RegionFunction -> Function[{x, y}, x^2 + y^3 > 2 x] ]

POSTED BY: Frank Kampas

It is just one of your inequalities but with an =

ContourPlot[x^3 - y^2 == 2 y, {x, -1, 1}, {y, -1, .1}]

enter image description here

POSTED BY: Sander Huisman
Reply to this discussion
Community posts can be styled and formatted using the Markdown syntax.
Reply Preview
Attachments
Remove
or Discard

Group Abstract Group Abstract