HP 33s User Manual page 69

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