The ▶ Command

convert.png

Command Summary

Converts an expression from one unit to another.

Command Syntax

expressionunits

Menu Location

Press [2nd][▶] to enter ▶: this is

  • [2nd][MODE] on a TI-89 or TI-89 Titanium
  • [2nd][Y] on a TI-92, TI-92 Plus, or Voyage 200

Calculator Compatibility

This command works on all calculators.

Token Size

2 bytes

The ▶ operator converts an expression to a different unit. Usually, this refers to the built-in units (such as _m (meters), _mph (miles per hour, etc.) which you can select from the UNITS menu.

To use it, you must first have the expression on the left in terms of some unit — this is done by multiplying it by that unit. For instance, "5 meters" is written as 5_m or 5*_m (where _m is the unit). You can combine units as well: for instance, 5_m^2 (5 square meters) or 30_km/_hr (30 kilometers per hour).

To convert that into a different unit, type ▶ and then a different unit to convert to (again, you can combine units). For instance, to convert 5 square meters to acres, type 5_m^2▶_acre. (Note: the result will always be expressed as a decimal)

:30_km/_hr▶_m/_s
           8.33333*_m/_s
:5_N▶_dyne
           500000.*_dyne

You can't use ▶ to convert between units of temperature (degrees Celsius to degrees Fahrenheit, for instance), since the calculator isn't sure if you mean absolute temperature or a change in temperature instead. Use the tmpCnv() and ΔtmpCnv() commands instead.

Advanced Uses

It's possible to define your own units as well: units are just any variable beginning with an underscore, and ▶ will perform just as well converting between those. There are two ways to go about it. The first is to define your units in terms of existing ones: for instance, you might define a furlong (one-eighth of a mile) as follows:

:1/8_mi→_furlong
           1/8*_mi
:110_yd▶_furlong
           .5*_furlong

The second method is to start with a unit or several units to keep undefined (for instance, _x). You can then define other units in terms of _x, and convert between them:
:5_x→_y
           5*_x
:3_y▶_x
           15.*_x
:10_x/_s▶_y/_s
           2.*_y/_s

Units are treated just like variables, except that they're universal across folders: you can have only one instance of _x, and you can access it as _x no matter which folder you're in. You can use this if you want to define a universal variable to access in any folder: for instance, if you define a program as _prgm(), you can run it with _prgm() from any folder.

Error Conditions

345 - Inconsistent units happens when converting between two units that measure different types of quantities (for instance, converting length to time).

Related Commands

See Also

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