Texas Instruments TI-89 User Manual - Page 290

• If the defaults are Area = _acre and Length = _m (meters), area results are shown with _acre units. • If you set Area = NONE, area results are shown with _m2 units. Note: NONE is not available for base categories such as Length and Mass that have no components. Creating Your Own User-Defined Units In any category, you can expand the list of available units by defining a new unit in terms of one or more pre-defined units. You can also use "standalone" units. Why Use Your Own Units? Some example reasons to create a unit are: • You want to enter length values in dekameters. Define 10_m as a new unit named _dm. • Instead of entering _m/_s2 as an acceleration unit, you define that combination of units as a single unit named _ms2. • You want to calculate how many times someone blinks. You can use _blinks as a valid unit without defining it. This "standalone" unit is treated similar to a variable that is not defined. For instance, 3_blinks is treated the same as 3a. Note: If you create a user-defined unit for an existing category, you can select it from the UNITS dialog box menu. But you cannot use 3 to select the unit as a default for displayed results. Constants and Measurement Units 290