Apple iWork '09 - Manual (Page 330)

Examples
=ASINH(27.2899171971277) returns 4.
=ASINH(SINH(1)) returns 1.
Related Topics
For related functions and additional information, see:
“ASIN” on page 329
“SIN” on page 336
“SINH” on page 337
“Listing of Trigonometric Functions” on page 326
“Value Types” on page 36
“The Elements of Formulas” on page 15
“Using the Keyboard and Mouse to Create and Edit Formulas” on page 26
“Pasting from Examples in Help” on page 41
ATAN
The ATAN function returns the inverse tangent (arctangent) of a number.
ATAN(num)
 num: A number. num is a number value.
Usage Notes
The ATAN function takes a tangent and returns the corresponding angle, Â
expressed in radians in the range –pi/2 to +pi/2. To see the resulting angle in
degrees instead of radians, wrap this function in the DEGREES function; that is,
=DEGREES(ATAN(num)).
Examples
=ATAN(1) returns the angle measure 0.785398163 radians (45 degrees), which has a tangent of 1.
=DEGREES(ATAN(1)) returns 45.
Related Topics
For related functions and additional information, see:
“ATAN2” on page 331
“ATANH” on page 332
330 Chapter 12 Trigonometric Functions