plotting two functions in geogebra

djt0607

Hi all,

I am wondering how I an plot two functions against each other in geogebra?

For example, suppose I have two functions and both are dependednt on time t

a(t) & b(t)

I wish to plot a(t) against b(t) for all time values from 0 - 1

How would I do this?

Thanks,

Regards,

djt

derb12

Just plot them one after the other eg
A(x)=3x-1
B(x)=x^2
And then zoom in on the x-axis so that you are just looking between 0 and 1

djt0607

Thanks for your reply.

That will only plot a(t) against t and draw another line of b(t) (against t).

I want a(t) on the y-axis against b(t) on the x-axis (or vice versa) and the graph plotted for the varying values of t

derb12

I dont know what you mean by plotting functions this way - it doesn't sound like you're plotting a function.
I see you've double posted on the LC forum and here so hope you get what you're looking for over there.

djt0607

Thanks again for your reply. Yes you can do it. I just did it manually anyways, so all is well and ends well.

Basically I had two functions. a(t) and b(t)

Lets say I want to find out the outputs for both functions when t=0.1.

I find a(0.1) and then b(0.1). Lets say I obtain 0.97 and 0.7

I do the same for when t=0.2

So I find a(0.2) and then b(0.2). Lets say I obtain 0.8 and 0.5

So I will have the two coordinate points

(0.97,0.7) for when t=0.1
and (0.8,0.5) for when t=0.2

I can then plot these coordinate points on a graph that will show a(t) against b(t) for varying values of t.

The two points may look something like this (assuming a(t) is the independent variable)...

b(t)
1| .
|
| .
|
|
|
|

---

a(t)
0 1

Geuze

I hope you're not a teacher.

If t is the independent variable, then it goes on the x axis.

You put t=0.1 and then t=0.2 into the two functions, okay.

But please note that your resulting co-ordinates should be of the form (0.1, f(0.1)) and (0.2, f(0.2)).

I hope that makes sense.

red_fox

Of course the result won't be a function, just a parameterised curve, with parameter t. I'm not experienced with geogebra but I can imagine something like plot (a(t),b(t)) for t=0..1 but I guess even ten points would give a good sense of the curve.

This is a perfectly common and sensible thing to do, and one of the more straightforward instances is in predator/prey population plots. I'm surprised you weren't met with better understanding (or maybe most just don't know how to do in Geogebra, like me!)

Edit, I'm thinking of a phase plot. Couldn't remember the name when I first posted.