Texas Instruments TI-89 User Manual - Page 247

Delayed Simplification for Certain Built-In Functions Usually, variables are automatically simplified to their lowest possible level before they are passed to a function. For certain functions, however, complete simplification is delayed until after the function is performed. Functions that Use Delayed Simplification Functions that use delayed simplification have a required var argument that performs the function with respect to a variable. These functions have at least two arguments with the general form: function(expression, var [, ... ]) Note: Not all functions that use a var argument use delayed simplification. For example: solve(x^2NxN2=0,x) d(x^2NxN2,x) ‰(x^2NxN2,x) limit(x2NxN2,x,5) For a function that uses delayed simplification: 1. The var variable is simplified to the lowest level at which it remains a variable (even if it could be further simplified to a non-variable value). 2. The function is performed using the variable. 3. If var can be further simplified, that value is then substituted into the result. Symbolic Manipulation 247