HP 38g Graphing Calculator - Manual (Page 76)

Tracing
Many aplets have a Trace mode. Trace mode is on when a
plot has just been drawn. When Trace mode is on, the
crosshairs cursor follows just the plotted points when you
press the Q or @ keys. The cursor traces the function. The
display also shows the current coordinate position (jc, y) of
the cursor.
If there is more than one curve displayed, press (T| or [Yl to
move between curves.
Note that tracing might not appear to exactly follow your plot
if the resolution (in Plot Setup view) is set to Faster. This is
because RES: FASTER plots in only every other column,
whereas tracing always uses every column.
In Function and Sequence Aplets : You can also scroll
(move the cursor) left or right beyond the edge of the display
window in Trace mode, giving you a view of more of the plot.
coordinates.
: FSiinn
crosshairs
cursor
3-12 Plotting and Exploring Functions