HP 33s Owner's Manual page 69

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