HP 50G, User Manual

Page: 394 / 887

Page 12-11
The PPAR variable
Press
J
to recover your variables menu, if needed. In your variables menu
you should have a variable labeled PPAR . Press
‚ @PPAR
to get the contents
of this variable in the stack. Press the down-arrow key, , to launch the stack
editor, and use the up- and down-arrow keys to view the full contents of PPAR.
The screen will show the following values:
PPAR stands for Plot PARameters , and its contents include two ordered pairs of
real numbers,
(-8.,-1.10797263281) and (2.,7.38905609893),
which represent the coordinates of the lower left corner and the upper right
corner of the plot, respectively. Next, PPAR lists the name of the independent
variable , X, followed by a number that specifies the increment of the
independent variable in the generation of the plot. The value shown here is the
default value, zero (0.), which specifies increments in X corresponding to 1 pixel
in the graphics display. The next element in PPAR is a
list containing first the
coordinates of the point of intersection of the plot axes , i.e., (0.,0.), followed by
a list that specifies the tick mark annotation on the x- and y-axes, respectively {#
10d # 10d}. Next, PPAR lists the type of plot that is to be generated, i.e.,
FUNCTION, and, finally, the y-axis label , i.e., Y.
The variable PPAR, if non-existent, is generated every time you create a plot.
The contents of the function will change depending on the type of plot and on
the options that you select in the PLOT window (the window generated by the
simultaneous activation of the
„
and
ò
(
B
) keys.
Inverse functions and their graphs
Let y = f(x) , if we can find a function y = g(x) , such that, g(f(x)) = x , then we say
that g(x) is the inverse function of f(x) . Typically, the notation g(x) = f
-1
(x) is
used to denote an inverse function. Using this notation we can write: if y = f(x),
then x = f
-1
(y). Also, f(f
-1
(x)) = x , and f
-1
(f(x)) = x .