Manpages - atan.3

atan, atanf, atanl - arc tangent function

  #include <math.h>

  double atan(double x);
  float atanf(float x);
  long double atanl(long double x);

Link with -lm.

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

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

On 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.

No errors occur.

For an explanation of the terms used in this section, see *attributes*(7).

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD, C89.

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

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