HP 15c - Manual (Page 26)

26 Section 2: Numeric Functions
Trigonometric Operations
Trigonometric Modes. The trigonometric functions operate in the
trigonometric mode you select. Specifying a trigonometric mode does not
convert any number already in the calculator to that mode; it merely tells
the calculator what unit of measure (degrees, radians, or grads) to assign a
number for a trigonometric function.
Pressing | D sets Degrees mode. No annunciator appears in the
display. Degrees are in decimal, not minutes-seconds form.
Pressing | R sets Radians mode. The RAD annunciator appears in
the display. In Complex mode, all functions (except : and ;) assume
values are in radians, regardless of the trigonometric annunciator displayed.
Pressing | g sets Grads mode. The GRAD annunciator appears in
the display.
Continuous Memory will maintain the last trigonometric mode selected. At
"power up" (initial condition or when Continuous Memory is reset), the
calculator is in Degrees mode,
Trigonometric Functions. Given x in the display (X-register):
Pressing Calculates
[
sine of x
|,
arc sine of x
\
cosine of x
|{
arc cosine of x
]
tangent of x
|/
arc tangent of x
Before executing a trigonometric function, be sure that the calculator is set
to the desired trigonometric mode (Degrees, Radians, or Grads).
Time and Angle Conversions
Numbers representing time (hours) or angles (degrees) can be converted by
the HP-15C between a decimal-fraction and a minutes-seconds format: