Assumptions is an option for functions such as Simplify, Refine and Integrate which specifies default assumptions to be made about symbolic quantities.
The default setting is Assumptions:>$Assumptions.
The assumptions can be equations, inequalities or domain specifications, or lists or logical combinations of these.
Assuming modifies $Assumptions and so modifies the value of default settings for Assumptions options.
x Reals can be used to specify that x should be treated as a real variable.
See Section 3.5.8.
See also: Assuming, $Assumptions, GenerateConditions, Integrate, Refine, Limit.
New in Version 3; modified in 5.0.