HP 33s - Manual (Page 69)

Real–Number Functions 4–5
Example:
Show that cosine (5/7) π radians and cosine 128.57° are equal (to four significant
digits).
Keys: Display: Description:
Ÿ { }  Sets Radians mode; RAD
annunciator on.
 5  7 ‘
)
 5/7 in decimal format.
| N z R
.
)  Cos (5/7) π.
Ÿ {} .
)  Switches to Degrees mode (no
annunciator).
128.57 R
.
)  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.