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ComputingCMath.h

atanl

Arc tangent function of one variable
+ View other versions (4)

Interface

#include <math.h>
double atan (double x)
long atanl (long double x)
float atanf (float x)

#include <complex.h>
complex atan (complex x)
double complex catan (double complex x)
float complex catanf (float complex x)
long double complex catanl (long double complex x)

Description

The atan function computes the principal value of the arc tangent of x, returning a value in the range [-\pi/2, +\pi/2]. The arc tangent is also often denoted as \tan^{-1}(x).

The complex inverse tangent is defined by:

Example:
Example - Arc tangent function of one variable
Workings
#include <stdio.h>
#include <math.h>
int main(void)
{
  double result, x = 0.6325;
  result = atan(x);
  printf("The arc sin of %lf is %lf\n", x, result);
}
Solution

Output:

The arc sin of 0.632500 is 0.563974

Special Values

atan ( ±0 ) returns ±0.

atan ( ±∞ ) returns ±\pi/2.

Standards

The atan function conforms to ISO/IEC 9899:1999(E).

Compatibility

DOSUNIXWindowsANSI CC++ only
atanl••
Real atan••••
Complex atan•••
Complex catan••