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atan, atanf, atanl - arc tangent function

#include<math.h>doubleatan(doublex);floatatanf(floatx);longdoubleatanl(longdoublex);Link with-lm. Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):atanf(),atanl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; orcc-std=c99

Theatan() function calculates the principal value of the arc tangent ofx; that is the value whose tangent isx.

On success, these functions return the principal value of the arc tangent ofxin radians; the return value is in the range [-pi/2, pi/2]. Ifxis a NaN, a NaN is returned. Ifxis +0 (-0), +0 (-0) is returned. Ifxis positive infinity (negative infinity), +pi/2 (-pi/2) is returned.

No errors occur.

C99, POSIX.1-2001. The variant returningdoublealso conforms to SVr4, 4.3BSD, C89.

acos(3),asin(3),atan2(3),carg(3),catan(3),cos(3),sin(3),tan(3)

This page is part of release 3.24 of the Linuxman-pagesproject. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2008-12-02 ATAN(3)