STO and COMPLEX : These are related to the memories and complex numbers. We will discuss
this later.
RCL and % : RCL is related to memories and we will discuss later. % is the percentage
function. To calculate 10% of 300 we do 300 ENTER 10 % which gives 30 as the answer.
Note that 300 remains in line y, so if you want to calculate 300 plus 10% you do 300 ENTER
10 % +
R↓ and π : We already discussed these. The first “rolls down” the stack and the other returns
π=3.14...
SIN and ASIN : These are the sine trigonometric function and inverse. The angle type is set up as
said before in the MODES menu. The default is degrees. ASIN is the inverse usually called
arcsine or sometimes sin
–1
(not to be confused with cosecant which is 1/sin). It is important to
remember that ASIN is not a real function since there is no single result. For example
sin(135°)=sin(45°)=√2/2 but the calculator gives always ASIN(√2/2)=45°. HP-42S will give a
complex number if the input of an arcsinus is bigger than 1 or smaller than -1.
COS and ACOS: These are the cosine trigonometric function and inverse.
TAN and ATAN: These are the tangent trigonometric function and inverse. Not all numbers can
have a result for tangent. For example tan(90°) goes to infinity. The HP-42S gives a big
number instead.
ENTER and ALPHA: The ENTER key does not need any comment. ALPHA is the alpha-
numeric menu used to enter letters instead of numbers. When you press ALPHA what
appears is
ABCDE FGHI JKLM NOPQ RSTUV WXYZ
These are sub-menus. If you press now ABCDE what you will have is
A B C D E
Then just pick the letter you want. But above you can see this symbol
▼▲. This symbol means
the menu has more than on line. You can access the other lines by pressing ▲ or ▼. In this
case there is just one more line with Ă, Å and Æ. If you press FGHI you will have F G H I,
etc. Among all calculators I know this is in my opinion the best way to enter letters! The main
ALPHA menu also has a
▼▲ symbol. The other line has the following submenus.
( [ { ← ↑ ↓ < = > MATH PUNC MISC
Much more than one will ever need! If you are inside a submenu and want to go back to the
main menu just press EXIT. Why is the ALPHA menu useful? Of course it is useful to label
programs and data in memory, but it is also useful to enter commands using the XEQ key!
For example XEQ “SIN” is the same of pressing the SIN key. The “” are called automatically
when pressing ALPHA and ENTER. XEQ “SINH” calculates the hyperbolic sine while
XEQ “OFF” turns the calculator off. Finally we must say that ALPHA is not always
needed! In some cases like XEQ and GTO (we will see this later) a simple ENTER will do.
Entering alphabetic text is even easier with Free42. Free42 allows you to just type on the
native keyboard when the ALPHA menu is activated.
x<>y and LASTx: We already talked about these.
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