atan2()

Computes the value of a tangent.

  #include <math.h>
  
  double atan2(double y, double x);
  
  float atan2f(float, float);
  
  long double atan2l(long double, long double);    

These functions return the arctangent of y / x, in radians from -pi to pi. If y and x are 0, then these functions set errno to EDOM and

  fpclassify(atan2(x))  
  

returns FP_NAN.

This facility may not be available on configurations of the EWL that run on platforms that do not have floating-point math capabilities.

#include <math.h>

#include <stdio.h>

int main(void)

{

double x = 0.5, y = -1.0;

printf("arccos (%f) = %f\n", x, acos(x));

printf("arcsin (%f) = %f\n", x, asin(x));

printf("arctan (%f) = %f\n", x, atan(x));

printf("arctan (%f / %f) = %f\n", y, x, atan2(y, x));

return 0;

}

Output:

arccos (0.500000) = 1.047198

arcsin (0.500000) = 0.523599

arctan (0.500000) = 0.463648

arctan (-1.000000 / 0.500000) = -1.107149