HP MLIB User's Guide Vol. 2 7th Ed.

Chapter 12 VMATH 815
The arctangent and quadrant function of the corresponding elements of two vectors vsAtan2, vdAtan2
Name vsAtan2, vdAtan2
The arctangent and quadrant function of the corresponding elements of two
vectors
Purpose vsAtan2 and vdAtan2 calculate the arctangent function of the quotient of
vector element pairs a(i)/b(i), in the range -Pi to Pi, using the signs of both
arguments to determine the quandrant of the result value:
y[i] = atan2(a[i],b[i]), for 0 <= i <= n-1
Usage VMATH:
#include <vmath.h>
void vsAtan2 (int n, const float a[ ], const float b[ ], float y [ ] ) ;
void vdAtan2 (int n, const double a [ ], const float b[ ], double y [ ] ) ;
VMATH8:
#include <vmath8.h>
void vsAtan2 (long long n, const float a[ ], const float b[ ], float y [ ] ) ;
void vdAtan2 (long long n, const double a [ ], const double b[ ], double
y [ ] ) ;
Input n Number of elements to be calculated.
a Array of length at least n, specifying the input vector of
numerators.
b Array of length at least n, specifying the input vector of
denominators.
Output y Array of length at least n, specifying the output vector.