Actually, I'm fairly certain that - no, wait. I was going to say that it was in the manual for the 89 somewhere, because I once had the formula for said graph, but that's wrong. I actually emailed TI about it and (whoa) somebody responded with the formula for the graph. I don't have it anymore, that was years ago with I still had a (gack) hotmail account.

If you want the formula, I suggest emailing TI's customer service or something similar to see if they'll send it to you.

-Fil

Here it is:


z(x,y)=20*cos((x^2+y^2)/4)/(x^2+y^2+pi)

With:

Eye theta: 20
Eye phi: 70
Eye psi: -.41
xmin: -5.
xmax: 5.
xgrid: 20.
ymin: -5.
ymax: 5.
ygrid: 20.
zmin: -1.2953
zmax: 6.3662
ncontour=1.

Happy? :p

I got:
z=when(x=0 and y=0,1,sin(sqrt(x^2+y^2))/sqrt(x^2+y^2))
xmin=ymin=-3*pi
xmax=ymax=3*pi
xgrid=ygrid=22
zmin=-1
zmax=1
Hidden surface drawmode

They both give you the same effect. The only dirrence is the second one, you cannot se through the wire, because f the hidden surface graphing. I am going to keep both thse on my VTI.

-W-

Damn it! You just made my vote false ;)
Actually, although the graph is in the ticalc.org logo, it's also used by TI on 89 cases.

still doesn't look the same. the other one curves down at the corners, yours curves up. and it just plain old looks different

Darn, I just tried it... you're right :(

No. I have heard the graph described as the 'water ripple' 3D graph. But I found on the internet somewhere that it takes about 45 minutes for a calc to make it...

V T I, my friend, V T I.

-W-

I got:
(1/(sqrt(x^2+y^2))*sin(sqrt(x^2+y^2)) *15-5

Where the *15-5 is added simply to make it fit better in the window.
so the basic concept is:
sin(sqrt(x^2+y^2))/(sqrt(x^2+y^2))

To give you a baic idea of what's going on, it's easier to see it in 2-dimensions.

sqrt(x^2+y^2)

can be considered plainly x in 2 dimensions.
So if you slopily convert the basic idea to 2-D.
you get:

sin(x)/x

and to make it look better in the window you can multiply it by 10 or so.

That's not sloppy boyo, that is perfect deductions.
And to make it fit better in the window....
....changing the window parameters is generally more legit.

Yeah, I used ZoomFit in the Zoom menu on my 89 to make it fit, and it works perfectly.

Um...the top "peak" is cut off...

That can easily be fixed by a slight adjustment of the *15-5 or the window settings.

No, it is the nature of the equation itself...the "peak" is undefined for some reason. I've already tried adjusting the "*15-5". sorry

Use when(x=0 and y=0,[coordinates of peak],[what you originally said])

I couldn't do it. But I have to say that it is a cool 3-D Wire Graph.

There's no way I can do that!

They seem really desperate for survey ideas. Maybe more people need to contribute them? And no, I can't reproduce the graph.

Twice I sent in a list of possible surveys. I guess they din't like them beacuse it was the same list twice. I have tried over and over again to get that graph. I've come close a few times but I gave up because I had other things to do.

I sent in the survey about wanting an open forum. I wish that they would have one, or at least put up my survey.

-W-