HP 50g Graphing Calculator - Manual (Page 392)

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10 by using 1\ @@@OK@@ 10@@@OK@@@. Next, press the soft key labeled @AUTO
to let the calculator determine the corresponding vertical range. After a couple
of seconds this range will be shown in the PLOT WINDOW-FUNCTION
window. At this point we are ready to produce the graph of ln(X). Press
@ERASE
@DRAW to plot the natural logarithm function.
To add labels to the graph press @EDIT L@)LABEL. Press @MENU to remove the
menu labels, and get a full view of the graph. Press L to recover the current
graphic menu. Press L
@)PICT to recover the original graphical menu.
To determine the coordinates of points on the curve press @TRACE (the cursor
moves on top of the curve at a point located near the center of the horizontal
range). Next, press (X,Y) to see the coordinates of the current cursor location.
These coordinates will be shown at the bottom of the screen. Use the right- and
left-arrow keys to move the cursor along the curve. As you move the cursor
along the curve the coordinates of the curve are displayed at the bottom of the
screen. Check that when Y:1.00E0, X:2.72E0. This is the point (e,1), since
ln(e) = 1. Press L to recover the graphics menu.
Next, we will find the intersection of the curve with the x-axis by pressing @)FCN
@ROOT. The calculator returns the value
Root: 1
, confirming that ln(1) = 0. Press
LL@)PICT @CANCL to return to the PLOT WINDOW – FUNCTION. Press `
to return to normal calculator display. You will notice that the root found in the
graphics environment was copied to the calculator stack.
Note: When you press J , your variables list will show new variables
called
@@@X@@ and @@Y1@@ .Press ‚@@Y1@@ to see the contents of this variable. You
will get the program << → X ‘LN(X)’ >> , which you will recognize as the
program that may result from defining the function ‘Y1(X) = LN(X)’ by using
„à. This is basically what happens when you @@ADD@! a function in the
PLOT – FUNCTION window (the window that results from pressing
ñ,
simultaneously if in RPN mode), i.e., the function gets defined and added to
your variable list.