|
|
HP-UX Reference Volume 4 of 5 > aatan2d(3M) |
|
NAMEatan2d(), atan2df() — degree-valued arctangent-and-quadrant functions DESCRIPTIONatan2d() is a degree-valued version of the atan2() function. It returns the arctangent of y/x, in the range -180 to 180, using the signs of both arguments to determine the quadrant of the return value. atan2df() is a float version of atan2d(); it takes float arguments and returns a float result. atan2d() and atan2df() are not specified by any standard, but atan2df() is named in accordance with the conventions specified in the "Future Library Directions" section of the ANSI C standard. To use these functions, compile either with the default -Ae option or with the -Aa and -D_HPUX_SOURCE options. Make sure your program includes <math.h>. Link in the math library by specifying -lm on the compiler or linker command line. RETURN VALUEIf y and x are +INFINITY, atan2d() returns 45. If y is +INFINITY and x is -INFINITY, atan2d() returns 135. If y is -INFINITY and x is +INFINITY, atan2d() returns -45. If y and x are -INFINITY, atan2d() returns -135. If y is zero and x is greater than zero, atan2d() returns zero. If y is zero and x is less than zero, atan2d() returns 180. If y is -zero and x is less than zero, atan2d() returns -180. If y is greater than zero and x is zero, atan2d() returns 90. If y is less than zero and x is zero, atan2d() returns -90. If y/x would overflow, atan2d() returns ±90. The result will be 90 if y is greater than zero and -90 if y is less than zero. If y/x after rounding would be smaller in magnitude than MINDOUBLE, atan2d() returns ±180 or zero. The result will be zero if x is greater than zero, 180 if x is less than zero and y is greater than zero, and -180 if x and y are both less than zero. If both x and y are zero, atan2d() returns NaN. If x or y is NaN, atan2d() returns NaN. If the correct value after rounding would be smaller in magnitude than MINDOUBLE, atan2d() returns zero. |
|