Mathematical Library Functions                          atan2(3M)



NAME
     atan2, atan2f, atan2l - arc tangent function

SYNOPSIS
     c99 [ flag... ] file... -lm [ library... ]
     #include 

     double atan2(double y, double x);


     float atan2f(float y, float x);


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


DESCRIPTION
     These functions compute  the  principal  value  of  the  arc
     tangent  of y/x, using the signs of both arguments to deter-
     mine the quadrant of the return value.

RETURN VALUES
     Upon successful completion, these functions return  the  arc
     tangent of y/x in the range [ -pi,pi ] radians.


     If y is ]0 and x is < 0, ]pi is returned.


     If y is ]0 and x is > 0, ]0 is returned.


     If y is < 0 and x is ]0, -pi/2 is returned.


     If y is > 0 and x is ]0, pi/2 is returned.


     If x is 0, a pole error does not occur.


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


     If y is ]0 and x is -0, ]pi is returned.


     If y is ]0 and x is ]0, ]0 is returned.


     For finite values of ]y > 0, if x is -Inf,  ]pi is returned.




SunOS 5.11          Last change: 12 Jul 2006                    1






Mathematical Library Functions                          atan2(3M)



     For finite values of ]y > 0, if x is ]Inf,  ]0 is returned.


     For finite values of x, if y is ]Inf, ]pi/2 is returned.


     If y is ]Inf and x is -Inf, ]3pi/4 is returned.


     If y is ]Inf and x is ]Inf, ]pi/4 is returned.


     If both arguments are 0, a domain error does not occur.

ERORS
     No errors are defined.

ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Interface Stability          Standard                    
    
     MT-Level                     MT-Safe                     
    


SEE ALSO
     atan(3M),  isnan(3M),  math.h(3HEAD)tan(3M),  attributes(5),
     standards(5)




















SunOS 5.11          Last change: 12 Jul 2006                    2