0
|
19948 Views
|
2 Replies
|
3 Total Likes
View groups...
Share

# Plotting x and y asymptotes of a rational function

Posted 9 years ago
 Hello, I've been trying to plot this rational function and illustrate the asymptotes of it, but I don't know how to get both the asymptotes plotted in together with the function. f(x_):=(3x-1)/(2x+6) 2 Replies
Sort By:
Posted 9 years ago
 You get a graph like that with f[x_] := (3 x - 1)/(2 x + 6); Plot[{f[x], 3/2}, {x, -11, 7}, Exclusions -> {x == -3}, ExclusionsStyle -> Red, PlotStyle -> {Black, Red}, PlotRange -> 10, AspectRatio -> Automatic] You can insert the labels with Epilog: f[x_] := (3 x - 1)/(2 x + 6); Plot[{f[x], 3/2}, {x, -11, 7}, Exclusions -> {x == -3}, ExclusionsStyle -> Red, PlotStyle -> {Black, Red}, PlotRange -> 10, AspectRatio -> Automatic, Epilog -> {Text[x == -3, {-5, -8}], Text[y == 1.5, {5, 2}]}] 
Posted 9 years ago
 Hi Torjus, I had a quick look, and there are a few ways of doing this. When you just plot the function like this:Plot[(3 x - 1)/(2 x + 6), {x, -10, 6}]you get an output with the vertical asymptote: You can then just add another function to plot of 1.5, like this: Plot[{(3 x - 1)/(2 x + 6), 1.5}, {x, -10, 6}] This is fine, but if you want both asymptotes to be a different graphics primitive we will have to try something else. You can also use GridLines, though I find this a bit clunky: Plot[(3 x - 1)/(2 x + 6), {x, -10, 6},GridLines->{{-3,0},{0,1.5}}] OK, so now we have both asymptotes, but still the vertical one from the original plot. To stop this from showing up use Exclusions (an option in plot): Plot[(3 x - 1)/(2 x + 6), {x, -10, 6},Exclusions->{x==-3},GridLines->{{-3,0},{0,1.5}}] Another way, and my preferred method, is to use the option Epilog to add a Line primitive onto the plot. You can then style the asymptotes separately to make them more clear: Plot[{(3 x - 1)/(2 x + 6), 1.5}, {x, -10, 6}, PlotStyle -> {Black, Red}, Exclusions -> {x == -3}, Epilog -> {Red, Line[{{-3, -100}, {-3, 100}}]}] From here, you can use labelling options to add in your asymptote labels.I hope this helps!Nia Knibbs Vaughan