atan2f man page on MacOSX

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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(�0, -0) returns �pi.

     atan2(�0, +0) returns �0.

     atan2(�0, x) returns �pi for x < 0.

     atan2(�0, x) returns �0 for x > 0.

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

     atan2(y, �0) 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 com‐
     puted 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 provided 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
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