Problem:
Using the TI-85 graphing calculator, graph the following function

for  x  in the interval  [-1, 4].

Visualization:

[Press here to see animation again!]

1. If you are not familiar with the graphing of functions on the TI-85, then first read the Initial Setup page from Little's Basic Guide to the TI-85.
2. Press the GRAPH key and then pick y(x)= by pressing the F1 key.
3. If necessary, keep pressing F4 key until only y1= appears on the screen.
4. Type in

(x + 1) (x < 2) + (2 - x) (x > 2)

and press the ENTER key.

5. You can get the  <  by pressing the 2nd, TEST and then the F4 key.
6. The range settings for the graph above is  [-1, 4] × [-3, 3].
The expression above uses two truth functions which are defined as follows:

and

The graph above is incorrect; a better approximation to the correct graph is

To obtain this,

1. Press the GRAPH key followed by the MORE key.
2. Press the F3 key to pick FORMT from the menu. You will see a menu:

3. Use the arrow keys to move to the item DrawDot on the third line and pres the ENTER key.
4. Press F5 to choose GRAPH to get the second graph above.

If you want to enter a piecewise defined function with more than two parts as, for example, the function

then type

3 (x < 2) + (x + 1)(2 < x and x < 5) + (-x)(5 < x)

where the term in the middle contains the function