Страницы справочника OS X

Эта страница руководства является частью версии 5.0 Инструментов XCode

Читать страницы руководства

ATAN2(3)                 BSD Library Functions Manual                 ATAN2(3)

NAME
     atan2 -- arc tangent function of two variables

SYNOPSIS
     #include <math.h>

     double
     atan2(double y, double x);

     long double
     atan2l(long double y, long double x);

     float
     atan2f(float y, float x);

DESCRIPTION
     The atan2() function computes the principal value of the arc tangent of y/x, using the signs of both
     arguments to determine the quadrant of the return value.

SPECIAL VALUES
     atan2(+-_, -_) returns +-pi.

     atan2(+-_, +_) returns +-0.

     atan2(+-_, x) returns +-pi for x < 0.

     atan2(+-_, x) returns +-0 for x > 0.

     atan2(y, +-_) returns +pi/2 for y > 0.

     atan2(y, +-_) returns -pi/2 for y < 0.

     atan2(+-y, -infinity) returns +-pi for finite y > 0.

     atan2(+-y, +infinity) returns +-0 for finite y > 0.

     atan2(+-infinity, x) returns +-pi/2 for finite x.

     atan2(+-infinity, -infinity) returns +-3*pi/4.

     atan2(+-infinity, +infinity) returns +-pi/4.

NOTES
     The atan2() function is used mostly to convert from rectangular (x,y) to polar (r,theta) coordinates
     that must satisfy x = r*cos theta and y = r*sin theta.  In general, conversions to polar coordinates
     should be computed thus:

           r    := hypot(x,y);  ... := sqrt(x*x+y*y)
           theta     := atan2(y,x).

VECTOR OPERATIONS
     If you need to apply the atan2() function to SIMD vectors or arrays, using the following functions pro-vided provided
     vided by the Accelerate.framework may give significantly better performance:

     #include <Accelerate/Accelerate.h>

     vFloat atan2f(vFloat y, vFloat x);
     void vvatan2f(float *z, const float *y, const float *x, const int *n);
     void vvatan2(double *z, const double *y, const double *x, const int *n);

SEE ALSO
     acos(3), asin(3), atan(3), cos(3), cosh(3), sin(3), sinh(3), tan(3), tanh(3), math(3),

STANDARDS
     The atan2() function conforms to ISO/IEC 9899:2011.

BSD                            December 11, 2006                           BSD