User Guide

Assumptions on Variables
To simplify problem solving, it is recommended that you always apply any
known assumptions to variables. You can impose assumptions using the
assume command. To apply assumptions for a single computation, use the
assuming command.
Note: The assume and assuming commands are not supported by the
RealDomain package.
The assume Command
You can use the assume command to set variable properties, for example,
x::real, and relationships between variables, for example, x < 0 or x < y.
For information on valid properties, refer to the ?assume help page. For in-
formation on the double colon (::) operator, refer to the ?type help page.
The assume command allows improved simplification of symbolic expres-
sions, especially multiple-valued functions, for example, computing the
square root.
To assume that x is a positive real number, use the following calling sequence.
Then compute the square root of .
>
The trailing tilde (~) on the name x indicates that it carries assumptions.
When you use the assume command to place another assumption on x, all
previous assumptions are removed.
>
3.6 Restricting the Domain • 117