acosh, acoshf, acoshl

Article
2015-04-28

Calculates the inverse hyperbolic cosine.

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

Parameters

x
Floating-point value.

Return Value

The acosh functions return the inverse hyberbolic 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.

Input	SEH Exception	_matherr Exception
± QNAN, IND, INF	none	none
x < 1	none	none

Remarks

When you use C++, you can call overloads of acosh that take and return float or long double values. In a C program, acosh always takes and returns double.

Requirements

Function	C header	C++ header
acosh, acoshf, acoshl	<math.h>	<cmath>

For additional 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

.NET Framework Equivalent

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

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