atan, atanl

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Header File

math.h

Category

Math Routines

Prototype

double atan(double x);
long double atanl(long double x);

Description

Calculates the arc tangent.

atan calculates the arc tangent of the input value.

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

Return Value

atan and atanl 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

#include <stdio.h>
#include <math.h>
int main(void)
{
   double result;
   double x = 0.5;
   result = atan(x);
   printf("The arc tangent of %lf is %lf\n", x, result);
   return(0);
}

Portability

	POSIX	Win32	ANSI C	ANSI C++
atan	+	+	+	+
atanl		+	+	+