C library function - atan()

Description

The C library function double atan(double x) returns the arc tangent of x in radians.

Declaration

Following is the declaration for atan() function.

double atan(double x)

Parameters

• x -- This is the floating point value.

Return Value

This function returns the principal arc tangent of x, in the interval [-pi/2,+pi/2] radians.

Example

The following example shows the usage of atan() function.

#include <stdio.h>
#include <math.h>

#define PI 3.14159265

int main ()
{
   double x, ret, val;
   x = 1.0;
   val = 180.0 / PI;

   ret = atan (x) * val;
   printf("The arc tangent of %lf is %lf degrees", x, ret);
   
   return(0);
}

Let us compile and run the above program, this will produce the following result:

The arc tangent of 1.000000 is 45.000000 degrees