HP -28S Manual page 36

Because of Algebraic Entry mode, pressing
G
wrote the character
+
in
the command line rather than executing the command.
Continue the expression.
o
SIN
Because of Algebraic Entry mode, pressing
0
wrote
l
in the com-
mand line, and pressing
SIN
wrote ::; I
t~
0::
in the command line,
rather than executing the commands.
Complete the expression and put it on the stack.
30 [ ENTER
I
' " " 3 : - : - - - - - - - - - - - - - ,
2:
1:
'(15+23)*SIN(30),
RI3rm:JDl!IIIiBDIEI3IEIl:I:J
The closing parenthesis
::0
and the closing delimiter ' are added for
you.
Evaluate the expression.
[EVALI
The expression is removed from the stack, and the result, 19, is re-
turned to level 1.
This completes the calculation:
(15
+
23) x sin 30°
=
19.
To perform a calculation that's already written as an expression, such
as in a textbook, it's easier to key in the expression and evaluate it.
Alternatively, to see the intermediate results of your calculation, or to
perform an on-going calculation, it's easier to calculate on the stack.
The results are the same.
The relationship between stack calculations and expressions is demon-
strated in chapter 4, "Repeating Calculations." In that chapter you
calculate on the stack, using names instead of numbers, to produce an
expression.
2: Doing Arithmetic 35