Drawfunc limits?

[jagboy]

We are doing a drawing project in math and I need to know how to put limits on functions. On the 83's it's like this: DrawF x^2/(x<2)(x>-4). Any ideas? I know it's a simple question and the project isn't exactly full of mathematic intensity but it's required.

JB

[mellamokb]

There are two options for implementing constraints on the TI-89. You can use the with bar ("|") like this (on the home screen):

Define y1(x) = 3x^2|2<x and x<3

on the regular 89 or

Define y1(x) = 3x^2|2<x<3

on the 89 Titanium (with AMS 3.10 or higher)

If you view the graph, you will see 3x^2 drawn only where x is between 2 and 3.

You can also use the 'When(' command, which is commonly used for step functions. The syntax of the 'When' command is

When(expression-to-test, value-if-true, value-if-false)

So if I typed "When(5>3, 2, 4)" on the homescreen, the calculator would output 2 because 5>3 is indeed true. I could rewrite my original equation using the 'When' function like this:

Define y1(x) = When(2<x and x<3, 3x^2, undef)

or with a TI89 Titanium with AMS 3.10 or higher:

Define y1(x) = When(2<x<3, 3x^2, undef)

Basically, this means the function should display 3x^2 only when x is between 2 and 3; otherwise, the function is undefined (and so wouldn't show up in a graph or be evaluated in a formula).

Hope this helps,

~ mellamokb

[jagboy]

Awesome! I just tried it and it worked! For some reason when using a drawfunc command in a program, using the "l" method doesn't work. Using "when(" worked flawlessly. I can't thank you enough.


JB

[mellamokb]

Glad to help, JB! I don't have my calculator with me, so I probably got the syntax wrong for the "|" command.

~ mellamokb