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HP-UX 11i Version 3: February 2007

Technical documentation

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atand(), atandf(), atandl(), atandw(), atandq() — degree-valued arctangent functions


#include <math.h>

double atand(double x);

float atandf(float x);

HP Integrity Server Only

long double atandl(long double x);

extended atandw(extended x);

quad atandq(quad x);


atand() returns the degree-valued arctangent of x, in the range -90 to 90.

atandf() is a float version of atand(); it takes a float argument and returns a float result.

Integrity Server Only

atandl() is a long double version of atand(); it takes a long double argument and returns a long double result.

atandw() is an extended version of atand(); it takes an extended argument and returns an extended result.

atandq() is equivalent to atandl() on HP-UX systems.


To use these functions, compile either with the default -Ae option or with the -Aa and -D_HPUX_SOURCE options.

To use (for Integrity servers) atandw() or atandq(), compile also with the -fpwidetypes option.

To use any of these functions, make sure your program includes <math.h>, and link in the math library by specifying -lm on the compiler or linker command line.

For more information, see the HP-UX floating-point guide for HP Integrity servers at the following site: http://www.hp.com/go/fp.


atand(±0) returns ±0.

If x is ±INFINITY, atand() returns ±90 respectively.

If x is NaN, atand() returns NaN.


No errors are defined.


These functions are not specified by any standard.

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