# Real Numbers; Complex Numbers - HP -28S Manual

Real Numbers
Real numbers represent numbers greater than _10
500
and less than
10
500 .
They are stored internally as a
mantissa
between 1 and
9.99999999999, a sign (positive or negative) for the mantissa, an
expo-
nent
between 0 and 499, and a sign for the exponent.
In Hours-Minutes-Seconds Format. You can use the commands
HMS
+
and HMS - to add and subtract numbers expressed as hours,
minutes, and seconds (or degrees, minutes, and seconds). For any
computation other than addition or subtraction, first use HMS- to
convert the numbers from HMS format to decimal degree format. (See
"TRIG" in the Reference Manual for details.)
Complex Numbers
Complex-number objects are ordered pairs of real numbers that repre-
sent the
real part
and the
imaginary part
of a complex number or the
coordinates of a point in a plane.
Rectangular and Polar Coordinates. In chapters 7 and 8 you used
complex numbers for plotting and digitizing; each complex number
represented
rectangular coordinates-that
is, distances along per-
pendicular axes.
Chapter 6 described
polar coordinates-a
gle-and used the commands R-P and P-R to convert between polar
and rectangular coordinates. You can use polar coordinates to key in
coordinates and to display results, but you must use rectangular co-
ordinates for calculations. The user function PSUM, described on
them, and reconverting them.
In AlgebraiC Objects. When you key in a complex number in an
algebraic object, you may need two pairs of parentheses, as in the
expression
I
S
I t·l
0:: 0::
0,
1 :; :;
I .
The outer pair of parentheses are re-
quired by the function
S
I
~l
0::
:;,
while the inner pair are delimiters
for complex numbers.
16: Objects
155  