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atan, atanl

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

Copy Code

    #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 |  | + | + | +

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