Assuming[assum, expr] evaluates expr with assum appended to $Assumptions, so that assum is included in the default assumptions used by functions such as Refine, Simplify and Integrate.
Assuming affects the default assumptions for all functions that have an Assumptions option.
The assumptions can be equations, inequalities or domain specifications, or lists or logical combinations of these.
Assumptions from nested invocations of Assuming are combined.
Assuming[assum, expr] is effectively equivalent to Block[$Assumptions = $Assumptions && assum, expr].
Assuming converts lists of assumptions , , ... to && && ... .
See Section 3.3.10.
See also: Block, Module, Refine, Reduce.
New in Version 5.0.