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   atan2f    ( 3 )

арктангенс функция двух переменных (arc tangent function of two variables)

Имя (Name)

atan2, atan2f, atan2l - arc tangent function of two variables

Синопсис (Synopsis)

#include <math.h>

double atan2(double y, double x); float atan2f(float y, float x); long double atan2l(long double y, long double x);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

atan2f(), atan2l(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE


Описание (Description)

These functions calculate the principal value of the arc tangent
       of y/x, using the signs of the two arguments to determine the
       quadrant of the result.

Возвращаемое значение (Return value)

On success, these functions return the principal value of the arc
       tangent of y/x in radians; the return value is in the range
       [-pi, pi].

If y is +0 (-0) and x is less than 0, +pi (-pi) is returned.

If y is +0 (-0) and x is greater than 0, +0 (-0) is returned.

If y is less than 0 and x is +0 or -0, -pi/2 is returned.

If y is greater than 0 and x is +0 or -0, pi/2 is returned.

If either x or y is NaN, a NaN is returned.

If y is +0 (-0) and x is -0, +pi (-pi) is returned.

If y is +0 (-0) and x is +0, +0 (-0) is returned.

If y is a finite value greater (less) than 0, and x is negative infinity, +pi (-pi) is returned.

If y is a finite value greater (less) than 0, and x is positive infinity, +0 (-0) is returned.

If y is positive infinity (negative infinity), and x is finite, pi/2 (-pi/2) is returned.

If y is positive infinity (negative infinity) and x is negative infinity, +3*pi/4 (-3*pi/4) is returned.

If y is positive infinity (negative infinity) and x is positive infinity, +pi/4 (-pi/4) is returned.


Ошибки (Error)

No errors occur.

Атрибуты (Attributes)

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

┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface Attribute Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │atan2(), atan2f(), atan2l() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘


Стандарты (Conforming to)

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

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


Смотри также (See also)

acos(3), asin(3), atan(3), carg(3), cos(3), sin(3), tan(3)