Retaining Calculated Values; The Num View Revisited - HP 39g Master Manual

Retaining calculated values

When you find an extremum or an intersection,
the point is remembered until you move again
even if it is not actually on a value that would
normally be accessible for the scale you have
chosen.
For example, if you find an intersection and then return to the menu
and choose Slope, the slope calculated will be for the intersection just found
rather than for the nearest pixel point. If you have recently found a root then
pressing the key and entering the value Root will return the cursor to it.
There are two ways to access these values. The first and simplest is via the
value stored in memory X. If you move from PLOT to the HOME view and type
X (using ALPHA) then the value it will contain will be the last position of the
cursor. If you just found a root or an intersection then this will be the value
displayed. The second way is via the reserved words of Root, Extremum,
Area, Slope and Isect. Typing any of these reserved words in any
situation will retrieve their last calculated values. If a value has not been
found yet then they will return zero.
This trick is particularly useful when calculating areas under or between
curves. See page 83.

The NUM view revisited

We saw earlier that the NUM view gives a
tabular view of the function.
It is possible to manipulate this view through
the NUM SETUP view.
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