Example.
Show
that
the cosine of (5/7)ir radians
and
the cosine of
128.57°
are
the
same.*
Keys:
Bl
MODES
|
{RD}
5fjNTCR]7[±]IQ0
fcosl
fllMODESl {DG}
128.57
rCQSl
Display:
-8.6235
-0.6235
Description:
Sets
Radians
mode;
RAD
annunciator
on.
Cos (5/7)ir.
Switches to Degrees
mode
(no annunciator)
and
calculates
cos
128.57°,
which
is
the
same as cos (5/7)ir.
Programming Note. Equations using inverse trigonometric functions
to determine an angle, 6, often look something like this:
6 =
arctan
(y/x).
If x = 0, then y
-s-
x is undefined, resulting in the error
DIVIDE
BY
0. For a program, then, it would be more reliable to
determine 6by a
rectangular
to
polar
conversion,
whichconverts
x,
y to
r,
6. See 'Coordinate Conversions,* later in this chapter.
'
Actually,
these
calculated
results
arethe sameonlyto
four
significant
digits
due to the inex
act representation of
a-.
(Press
jl]|
SHOW
Ito see more digits.)
58
4:
Real-Number
Functions
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