The Negative Key; The Chars Key - HP 39g Master Manual

An alternative to using the ANS key is to use the History facility and the
function. This is discussed on page 43.

The negative key

Another important key is the (-) key (shown right).
If you want to calculate the value of (say)
you must use the (-) key before the 2 and the 9 rather than the subtract
key. If you press the subtract key before the 2 instead of the (-) key, then
the calculator will enter instead: Ans - 2, meaning, subtract 2 from the
previous answer. Similarly, entering 'subtract, subtract 9' instead of 'subtract
(-) 9' will give an error message of "Invalid syntax", meaning it does not make
mathematical sense to have two subtract signs instead of a subtract of a
negative.
The reason for the Ans - 2 is that a subtract cannot start a 'sentence' in
mathematics, while a negative sign can. Since the subtract can't come first,
the calculator decides that you must have intended to subtract from the
previous answer. Hence the sudden appearance of an Ans. This occurs at
other times too. One of the most common
CHARS
The key
The next important key is the CHARS key (above VARS). This key is used to
access all of the many characters that are used occasionally but not often
enough to bother putting on the keyboard.
Pressing SHIFT CHARS will pop up the screen
above right. One of the screen keys is set to
be a 'Page Down' key (
access to two more pages of characters.
These special characters are obtained by
pressing the screen key labeled
can press as many times as you need to
in order to obtain multiple characters. When
you have as many as you need, press the
key.
− − −
2 ( 9)
), and will give
. You
33
then