# Truth Plots - HP 50g User Manual

Graphing calculator.

## Truth plots

Truth plots are used to produce two-dimensional plots of regions that satisfy a
certain mathematical condition that can be either true or false. For example,
suppose that you want to plot the region for X^2/36 + Y^2/9 < 1,
proceed as follows:
Press „ô, simultaneously if in RPN mode, to access to the PLOT SETUP
window.
Change
TYPE
Press ˜ and type {'(X^2/36+Y^2/9 < 1)','(X^2/16+Y^2/9 > 1)'}
@@@OK@@@ to define the conditions to be plotted.
The cursor is now in the
variable, or change it to 'X' if needed.
Press „ò, simultaneously if in RPN mode, to access the PLOT window
(in this case it will be called PLOT WINDOW – TRUTH window). Let's keep
the default value for the window's ranges:
4.0 (To
-3.9
Note: if the window's ranges are not set to default values, the quickest way to
reset them is by using L@RESET@ (select Reset all) @@@OK@@@ L.
Press @ERASE @DRAW to draw the truth plot. Because the calculator samples the
entire plotting domain, point by point, it takes a few minutes to produce a
truth plot. The present plot should produce a shaded ellipse of semi-axes 6
and 3 (in x and y, respectively), centered at the origin.
Press @EDIT L @LABEL @MENU to see the graph with labels.
parameters are such that you only see half of the labels in the x-axis. Press
L to recover the menu. Press L@) P ICT to recover the original graphics
Press (X,Y) to determine coordinates of any point on the graph. Use the
arrow keys to move the cursor about the region plotted. At the bottom of
the screen you will see the value of the coordinates of the cursor as (X,Y).
Press L@) C ANCL to return to the PLOT WINDOW environment. Then, press
You can have more than one condition plotted at the same time if you multiply
the conditions. For example, to plot the graph of the points for which X
2
Y
/9 < 1, and X
to
.
Truth
Indep
reset them use L @RESET (select Reset all) @@OK@@ L).
2
2
/16 + Y
/9 > 1, use the following:
field. Leave that as 'X' if already set to that
H-View: -6.5 6.5, V-View:
The window
2
/36 +
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