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/*************************************************************************
 * trig.c - math utilities library
 *
 * Mike Dixon RAP NCAR Boulder CO USA
 *
 * Nov 2008
 *
 ***************************************************************************/

#include <rapmath/trig.h>

/***********************************************
 * compute sin and cos together for efficiency
 */

void rap_sincos(double radians, double *sinVal, double *cosVal)
  
{
  
  double cosv, sinv, interval;

  /* compute cosine */

  cosv = cos(radians);
  *cosVal = cosv;

  /* compute sine magnitude */

  sinv = sqrt(1.0 - cosv * cosv);

  /* set sine sign from location relative to PI */

  interval = floor(radians / M_PI);
  if (fabs(fmod(interval, 2.0)) == 0) {
    *sinVal = sinv;
  } else {
    *sinVal = -1.0 * sinv;
  }

}

/**************************************************
 * compute atan2, setting result to 0 allowing for
 * floating point underflow
 */

double rap_atan2(double y, double x)
  
{
   
  if ((fabs(y - 0.0) < 1.0e-9) && (fabs(x - 0.0) < 1.0e-9)) {
    return 0;
  }

  return atan2(y, x);

}