| .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
| .\" |
| .\" Permission is granted to make and distribute verbatim copies of this |
| .\" manual provided the copyright notice and this permission notice are |
| .\" preserved on all copies. |
| .\" |
| .\" Permission is granted to copy and distribute modified versions of this |
| .\" manual under the conditions for verbatim copying, provided that the |
| .\" entire resulting derived work is distributed under the terms of a |
| .\" permission notice identical to this one. |
| .\" |
| .\" Since the Linux kernel and libraries are constantly changing, this |
| .\" manual page may be incorrect or out-of-date. The author(s) assume no |
| .\" responsibility for errors or omissions, or for damages resulting from |
| .\" the use of the information contained herein. The author(s) may not |
| .\" have taken the same level of care in the production of this manual, |
| .\" which is licensed free of charge, as they might when working |
| .\" professionally. |
| .\" |
| .\" Formatted or processed versions of this manual, if unaccompanied by |
| .\" the source, must acknowledge the copyright and authors of this work. |
| .\" |
| .\" References consulted: |
| .\" Linux libc source code |
| .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) |
| .\" 386BSD man pages |
| .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) |
| .\" Modified 2002-07-27 by Walter Harms |
| .\" (walter.harms@informatik.uni-oldenburg.de) |
| .\" |
| .TH ATAN 3 2002-07-27 "" "Linux Programmer's Manual" |
| .SH NAME |
| atan, atanf, atanl \- arc tangent function |
| .SH SYNOPSIS |
| .nf |
| .B #include <math.h> |
| .sp |
| .BI "double atan(double " x ); |
| .br |
| .BI "float atanf(float " x ); |
| .br |
| .BI "long double atanl( long double " x ); |
| .sp |
| .fi |
| Link with \fI\-lm\fP. |
| .SH DESCRIPTION |
| The |
| .BR atan () |
| function calculates the arc tangent of \fIx\fP; that is |
| the value whose tangent is \fIx\fP. |
| .SH "RETURN VALUE" |
| The |
| .BR atan () |
| function returns the arc tangent in radians and the |
| value is mathematically defined to be between \-PI/2 and PI/2 |
| (inclusive). |
| .SH "CONFORMING TO" |
| SVr4, POSIX.1-2001, 4.3BSD, C89. |
| The |
| .I float |
| and |
| .I "long double" |
| variants are C99 requirements. |
| .SH "SEE ALSO" |
| .BR acos (3), |
| .BR asin (3), |
| .BR atan2 (3), |
| .BR carg (3), |
| .BR catan (3), |
| .BR cos (3), |
| .BR sin (3), |
| .BR tan (3) |