acosh, acoshf, acoshl

Calculates the inverse hyperbolic cosine.

Syntax

double acosh( double x );
float acoshf( float x );
long double acoshl( long double x );
#define acosh(X) // Requires C11 or higher

float acosh( float x );  // C++ only
long double acosh( long double x );  // C++ only

Parameters

x
Floating-point value.

Return value

The acosh functions return the inverse hyperbolic cosine (arc hyperbolic cosine) of x. These functions are valid over the domain x ≥ 1. If x is less than 1, errno is set to EDOM, and the result is a quiet NaN. If x is a quiet NaN, indefinite, or infinity, the same value is returned.

Remarks

When you use C++, you can call overloads of acosh that take and return float or long double values. In a C program, unless you're using the <tgmath.h> macro to call this function, acosh always takes and returns double.

If you use the <tgmath.h> acosh() macro, the type of the argument determines which version of the function is selected. See Type-generic math for details.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

For more compatibility information, see Compatibility.

Example

// crt_acosh.c
// Compile by using: cl /W4 crt_acosh.c
// This program displays the hyperbolic cosine of pi / 4
// and the arc hyperbolic cosine of the result.

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

int main( void )
{
   double pi = 3.1415926535;
   double x, y;

   x = cosh( pi / 4 );
   y = acosh( x );
   printf( "cosh( %f ) = %f\n", pi/4, x );
   printf( "acosh( %f ) = %f\n", x, y );
}

cosh( 0.785398 ) = 1.324609
acosh( 1.324609 ) = 0.785398

See also

Math and floating-point support
asinh, asinhf, asinhl
atanh, atanhf, atanhl
cosh, coshf, coshl
sinh, sinhf, sinhl
tanh, tanhf, tanhl