Maple 9 Learning Guide - Maplesoft

174 • Chapter 6: Evaluation and Simplification> simplify( % );sin(x)cos(x)You can also use the convert command to perform structural manipulationson Maple objects. See 6.3 Structural Manipulations.6.2 AssumptionsThere are two means of imposing assumptions on unknowns.• To globally change the properties of unknowns, use the assume facility.• To perform a single operation under assumptions on unknowns, usethe assuming command.The assume facility and assuming command are discussed in the followingsubsections. For more information on these commands, refer to the?assume and ?assuming help pages.The assume FacilityThe assume facility is a set of routines for dealing with properties ofunknowns. The assume command allows improved simplification of symbolicexpressions, especially with multiple-valued functions, for example,the square root.> sqrt(a^2);√a 2Maple cannot simplify this, as the result is different for positive andnegative values of a. Stating an assumption about the value of a allowsMaple to simplify the expression.> assume( a>0 );> sqrt(a^2);a~The tilde (~) on a variable indicates that an assumption has beenmade about it. New assumptions replace old ones.