Even the best calculating machine is only as good as its input. When using the TI-83 Plus graphing calculator, you might make one of these eight common errors.

## Use [–] instead of [(-)] to indicate that a number is negative

If you press [–] instead of [(-)] at the beginning of an entry, the calculator assumes you want to subtract what comes after the minus sign from the previous answer. If you use [–] instead of [(-)] in the interior of an expression to denote a negative number, the calculator responds with the ERR: SYNTAX error message.

## Indicate the order of operations incorrectly by using parentheses

When evaluating expressions, the order of operations is crucial. To the calculator, for example, -32 equals –9. This may come as quite a surprise to someone expecting the more standard evaluation, where (-3)2 equals 9.

The calculator first performs the operation in parentheses, then it squares the number, and after that, it performs the unary operation of negating a number. Unless you’re careful, this won’t provide the answer you’re looking for. To guard against this error, you may want to review the detailed list of the order in which the calculator performs operations.

Also, when graphing rational functions, users who are new to the calculator often make the basic mistake of omitting the parentheses that must be used to set the numerator apart from the denominator.

## Improperly enter the argument for menu functions

If an argument is improperly entered, a menu function won’t work. A prime example is the fMin function housed in the Math MATH menu. Do you remember what to place after this function so you can use it? If you don’t, you get the ERR: ARGUMENT error message.

Texas Instruments offers a really invaluable (and free!) application called Catalog Help that you can install on your calculator. It reminds you of the appropriate argument that each function requires.

## Enter an angle in degrees while in Radian mode

Actually, you can do so legitimately, but you have to let the calculator know that you’re overriding the Angle mode by placing a degree symbol after your entry.

## Graph trigonometric functions while in Degree mode

This, too, is a mistake unless you do it just right: In the Window editor you have to set the limits for the x-axis as

Pressing [ZOOM][7] or [ZOOM][0] to have the calculator graph the function using the ZTrig or ZoomFit command produces similar results. But this works when you’re graphing pure trig functions such as sin x. If you’re graphing something like sin x + x, life is a lot easier if you graph it in Radian mode.

## Graph functions when Stat Plots are active

If you get the ERR: INVALID DIM error message when you graph a function, this is most likely caused by a Stat Plot that the calculator is trying to graph along with your function.

## Graph Stat Plots when functions or other Stat Plots are active

If you get the ERR: INVALID DIM error message when you graph a Stat Plot, this is most likely caused by a function or another Stat Plot that the calculator is trying to graph along with your function.

## Set the window inappropriately for graphing

If you get the ERR: WINDOW RANGE error message when graphing functions, this is most likely caused by setting

or by setting

in the Window editor.