atan - Online Linux Manual PageSection : 3
Updated : 2023-02-05
Source : Linux man-pages 6.03

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NAMEatan, atanf, atanl − arc tangent function

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LIBRARYMath library (libm, −lm)

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SYNOPSIS#include <math.h>double atan(double x); float atanf(float x); long double atanl(long double x);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): atanf(), atanl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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DESCRIPTIONThese functions calculate the principal value of the arc tangent of x; that is the value whose tangent is x.

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RETURN VALUEOn success, these functions return the principal value of the arc tangent of x in radians; the return value is in the range [−pi/2, pi/2]. If x is a NaN, a NaN is returned. If x is +0 (−0), +0 (−0) is returned. If x is positive infinity (negative infinity), +pi/2 (−pi/2) is returned.

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ERRORSNo errors occur.

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ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7). InterfaceAttributeValue atan(), atanf(), atanl() Thread safetyMT-Safe

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STANDARDSC99, POSIX.1-2001, POSIX.1-2008. The variant returning double also conforms to SVr4, 4.3BSD.

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SEE ALSOacos(3), asin(3), atan2(3), carg(3), catan(3), cos(3), sin(3), tan(3) 0

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