C Programming/math.h/atan

atan is a function in math.h. It computes arc tangent. It returns the principal value of the arc tangent of x, expressed in radians. In trigonometrics, arc tangent is the inverse operation of tangent. Note that because of sign ambiguity, function cannot determine in which quadrant the angle falls only by its tangent value. To determine quadrant, we can use atan2. Return value of this function is principal arc tangent of x, in the interval [-pi/2,+pi/2] radians.

Syntax

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

Here, x is Floating point value.

Example

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

#define PI 3.14159265

int main(void)
{
  double param, result;
  param = 1.0;
  result = atan(param) * 180 / PI;
  printf("The arc tangent of %lf is %lf degrees\n", param, result );
  return 0;
}

Output

The arc tangent of 1.000000 is 45.000000 degrees.

External links

• C++ reference for std::atan