HP 35s

Real–Number Functions 4-5
Example:
Show that cosine (5/7)π radians and cosine 128.57° are equal (to four significant
digits).
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:   .
Keys: Display: Description:
9()
Sets Radians mode; RAD
annunciator on.


5/7 in decimal format.
   

Cos (5/7)π.
9()

Switches to Degrees mode (no
annunciator).



Calculates cos 128.57°, which is
the same as cos (5/7)π.