Parametric equations TI-89

[TrueTears]

When I try to sketch this parametric equation on my TI-89:

xt1 = 2cos(t)
yt1 = 3sin(t)

the calc manages to sketch a ellipse but it does like 1000000 crazy revolutions and makes it look really "fat and thick"

I have it set in radians mode.

But when it's in degree mode, it sketches a perfectly smooth ellipse but it shouldn't be in degree mode...

Anyone else get this? Or does it sketch a smooth 1 ellipse?

[homghomg1]

Go to window and try reducing the max value for T, it's probably too high so the cycle repeats itself over and over

[TrueTears]

Yeah I've tried, the period is for both of those and I put and nothing even appears

So I put and it looks like this: With straight "sides" and looks like it's trying to "form" an ellipse rofl

[homghomg1]

hmm then i would say your Tstep is too high
mine is set at pi/24
other than that, i don't know, sorry

[TrueTears]

hmm then i would say your Tstep is too high
mine is set at pi/24
other than that, i don't know, sorry

ohhh it fixed it!! thanks!

I set mine to pi/24 as well

so what is "tstep"? How do I know what to set it to for diff graphs?

[Mao]

That's the interval at which the calculator evaluates the points.

E.g drawing a circle, you could evaluate two points according to a set for equations, but that would just be two points, not a circle. You could evaluate 5 points, but that'll be a pentagon. As you take more points, the closer it'll look to a circle.

Much the same thing here, if t_step is large, your graph will be crude. To get a smoother curve, you need to evaluate the function at smaller intervals.

[TrueTears]

That's the interval at which the calculator evaluates the points.

E.g drawing a circle, you could evaluate two points according to a set for equations, but that would just be two points, not a circle. You could evaluate 5 points, but that'll be a pentagon. As you take more points, the closer it'll look to a circle.

Much the same thing here, if t_step is large, your graph will be crude. To get a smoother curve, you need to evaluate the function at smaller intervals.

Oh right I see, thanks for that Mao!

[Hooligan]

My calc. graphs it up normal.
I just hit F2 6: ZoomStd after putting in the equations. Not sure if that's any help now, though.  :laugh:

[arthurk]

you can graph parametric?
wow i was never taught this. Hows it go?

[Mao]

In "Mode", in the first option, change from "function" to "parametric"

[kdgamz]

In "Mode", in the first option, change from "function" to "parametric"

i did that for my ti 89 and typed in xt1= sin(t), yt1=cos(t)....

but i didnt get a graph?

wat do i do??/

EDIT: dont worry.........window settings

[arthurk]

Is there anyway to define the domain of the parametric?

[TrueTears]

Is there anyway to define the domain of the parametric?

After each parametric equation type "| t = something "