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: