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Evaluation
When text has been entered and converted into an expression, the normal action is to call the
automatic simplifier on it. This converts the raw expression to be converted
into a standard form. This process includes doing arithmetic on purely numeric subexpressions. Most expressions
which can be evaluated to a pure number will be replaced by that number. For example sin(0) will be
replaced by 0.
Other functions cause operations to be performed on their arguments, returning a new result. The simplification
procedure includes the processing of these functions. For example, the function abs will attempt to
return the absolute value of its argument. abs(-3) and abs(3) both return the
value 3.
Commands
There is a small group of commands which are acted on without calling the simplifier first. These are distinct from normal functions, as they need to be acted upon outside of the context of automatic simplification:
showpoly assumes that its first operand is a polynomial and creates an expression that causes the polynomial to be shown in a form that highlights its structure. Similarly, showseries assumes that its first operand represents a power series, and shows this in a suitable format. These behaviours only occur when these commands are not part of a larger expression. When embedded in an expression, these two commands have no effect.
assign gives a value to a symbol. However, this is more conveniently done by using the assignment operator ':=', For example:
a := 5 gives the symbol a the value 5. From now on, when the
symbol a is looked at by the automatic simplifier, it will be replaced by its
value, 5.
unassign undoes the assignment of a value to a symbol.
how is used after using integrate to find the integral of an expression. The
command how() displays a brief description of how the integral was obtained.