atan, atanl

raw OCR

Calculates the arc tangent.

Defined in header <math.h>

Syntax

Real versions:                             Complex version:
#include <math.h>                          #include <complex.h>
double atan(double x);                     complex atan(complex  x)
long double atanl(long double x);

Portability

	DOS	UNIX	Windows	ANSI C	C++ only
atanI	■		■
Real atan	■	■	■	■
Complex atan	■		■		■

Remarks

atan calculates the arc tangent of the input value.

atan! is the long double version; it takes a long double argument and returns a long double result.

The complex inverse tangent is defined by

atan(z) = -0.5 i log((l + z z)/(l - i z))

Return value

atan and atanI of a real argument return a value in the range -pi/2 to pi/2.

Error handling for these functions can be modified through the functions matherr and _matherrl.

Example

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

int main(void)
{
   double result, x   0.5;
   result = atan(x);
   printfC'The arc tangent of %lf is %lf\n", x, result);
return(0);

Differences from modern implementations

Nothing recorded yet.

Modern references

These are search links, not yet checked by hand.

Extraction notes

heading `atan, atani` read as `atan, atanl`

Stable link: /3.1/math.h/atan/ · short form /3.1/atan/