HP 35s Scientific Calculator - Manual (Page 78)

4-4 Real–Number Functions
Setting the Angular Mode
The angular mode specifies which unit of measure to assume for angles used in
trigonometric functions. The mode does not convert numbers already present (see
"Conversion Functions" later in this chapter).
360 degrees = 2 π radians = 400 grads
To set an angular mode, press
9
. A menu will be displayed from which you
can select an option.
Trigonometric Functions
With x in the display:
Option Description Annunciator

Sets degree mode, which uses decimal
degrees rather than hexagesimal degrees
(degrees, minutes, seconds)
none

Sets radian mode
RAD

Sets gradient mode
GRAD
To Calculate: Press:
Sine of x. 
Cosine of x. 
Tangent of x. 
Arc sine of x.  
Arc cosine of x.  
Arc tangent of x.  
Note
Calculations with the irrational number π cannot be expressed
exactly by the 15–digit internal precision of the calculator. This is
particularly noticeable in trigonometry. For example, the
calculated sin
π (radians) is not zero but –2.0676 × 10 –13 , a very
small number close to zero.