HP 33S - Page 69

Real–Number Functions
4–5
File name 33s-E-Manual-1008-Publication(1st).doc Page : 386
Printed Date : 2003/10/8 Size : 13.7 x 21.2 cm
Example:
Show that cosine (5/7)
π
radians and cosine 128.57° are equal (to four significant
digits).
Keys: Display: Description:
Ý
{

}

Sets Radians mode; RAD
annunciator on.
Ë
5
Ë
7
Ï

5/7 in decimal format.
º j ¸ n

Cos (5/7)
π
.
Ý
{

}

Switches to Degrees mode (no
annunciator).
128.57
n

Calculates cos 128.57°, which
is the same as cos (5/7)
π
.
Programming Note:
Equations using inverse trigonometric functions to determine an angle
θ
, often look
something like this:
θ
= arctan (y
/
x).
If x = 0, then y
/
x is undefined, resulting in the error:
  
. For a program,
then, it would be more reliable to determine
θ
by a rectangular to polar conversion,
which converts (x,y) to (r,
θ
). See "Coordinate Conversions" later in this chapter.
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