Syntax

#include <math.h>
double atan(double x);
double atan2(double y, double x);

atan and atan2 calculate the arctangent of x and y/x, respectively.

atan returns a value in the range -pi/2 to pi/2 radians. atan2 returns a value in the range -pi to pi radians. If both arguments of atan2 are zero, the function sets errno to EDOM, and returns a value of 0.

This example calculates arctangents using the atan and atan2 functions.

#include <math.h>

int main(void)
{
   double a,b,c,d;

   c = 0.45;
   d = 0.23;
   a = atan(c);
   b = atan2(c, d);
   printf("atan( %lf ) = %lf\n", c, a);
   printf("atan2( %lf, %lf ) = %lf\n", c, d, b);
   return 0;

   /****************************************************************************
      The output should be:

      atan( 0.450000 ) = 0.422854
      atan2( 0.450000, 0.230000 ) = 1.098299
   ****************************************************************************/
}

• acos
  
• asin
  
• cos
  
• cosh
  
• sin
  
• sinh
  
• tan
  
• tanh

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