HP (Hewlett-Packard) 35s Calculator User Manual


 
6-10 Entering and Evaluating Equations
Expressions. The equation does not contain an "=". For example, x
3
+ 1
is an expression.
When you're calculating with an equation, you might use any type of equation —
although the type can affect how it's evaluated. When you're solving a problem for
an unknown variable, you'll probably use an equality or assignment. When you're
integrating a function, you'll probably use an expression.
Evaluating Equations
One of the most useful characteristics of equations is their ability to be evaluated
to generate numeric values. This is what enables you to calculate a result from an
equation. (It also enables you to solve and integrate equations, as described in
chapters 7 and 8).
Because many equations have two sides separated by "=", the basic value of an
equation is the difference between the values of the two sides. For this calculation,
"=" in an equation is essentially treated as "–". The value is a measure of how well
the equation balances.
The HP 35s has two keys for evaluating equations:
and . Their
actions differ only in how they evaluate assignment equations:
returns the value of the equation, regardless of the type of equation.
returns the value of the equation — unless it's an assignment–type
equation. For an assignment equation,
returns the value of the right
side only, and also "enters" that value into the variable on the left side — it
stores the value in the variable.
The following table shows the two ways to evaluate equations.