followed by HIST(CMD). A box called a choose box with your last four typed entries is shown. With (1+1)/5
selected, press the OK menu key followed by ENTER. This time, the result is .4. As a general rule, you can think of exact mode
solutions, R= , as combinations of fractions, integers, square roots, equations and values of PI. In approximate mode, R~,
everything is evaluated to a single, numerical answer.
Press the UP cursor key and observe how line two, above the highlight, now displays (1.+1.)/5., and line four displays (1+1)/5. The
extra periods after the numbers indicate approximate mode instead of exact mode. We will elaborate on this difference later. Press
CANCEL followed by the CLEAR menu key. Your stack is now cleared. For more information about creating and entering basic
expressions, see Chapter 2 of the HP 50g Graphing Calculator User's Manual or the HP 50g Graphing Calculator User's Guide.
The 50g comes from a history of calculators designed specifically for engineers and mathematicians. As such, it has very powerful tools
that permit you to enter, work with, and solve math problems quickly and efficiently. One of these tools is Reverse Polish Notation, (RPN).
RPN's greatest strength is that it lets you work out problems one small piece at a time. You don't have to type everything into a long equa-
tion and worry about using parentheses to set the order of operation. Because the 50g comes from a line of calculators that used RPN
exclusively, the calculator is easier to use and functions most effectively in RPN mode.
Let's change a few settings on our unit and get into RPN mode. Press the MODE key. A screen called an Input Form appears. These
full screen forms are used for a variety of tasks. On this screen, titled, Calculator Modes, many basic settings are shown. To begin,
press the FLAGS menu key. Press the UP cursor key until you reach 1 17 CHOOSE boxes. Press the CHK menu key to toggle to Soft
Menu. Press ENTER to return to the input form.
Press the UP cursor key five times. Notice how the menu and help text directly above the menu changes as you select different fields.
Once back on the first field, see how Algebraic is selected. Press the CHOOS menu key and a Choose Box appears (see Figure 4).
Press the DOWN cursor key to select RPN, then press ENTER. RPN appears in the first field, and it now will be the active operating
mode when the input form is closed. Choose boxes in input forms can also be changed by pressing
Press this key a few times and note how it toggles between RPN and Algebraic. With RPN selected, press ENTER again to save
your settings and exit the input form.
a field highlighted.