C acosh()

The acosh() function defined in the math.h header file. It helps to return the arc hyperbolic cosine value of the given number in radians. The arc hyperbolic cosine means inverse hyperbolic cosine value.

double acosh(double x); #where x can be in int, float or long double

Also, two functions acoshf() and acoshl() were used with type float and long double respectively.

float acoshf(float x); 
long double acoshl(long double x); 

acosh() Parameters:

The acosh() function takes a single parameter in the range x ≥ 1. Using cast operator we can explicitly convert the type to double to find the arc hyperbolic cosine of type int, float, or long double.

Parameter Description Required / Optional
double value A double value greater than or equal to 1  (x ≥ 1) Required

acosh() Return Value

The return value of acosh() function is a number greater than or equal to 0  in radians.

Input Return Value
x ≥ 1 a number greater than or equal to 0
x < 1 NaN (not a number)

Examples of acosh()

Example 1: Working of acosh() function in C?

#include <stdio.h>
#include <math.h>
int main()
    const double PI =  3.1415926;
    double v, output;

    v =  5.9;
    output = acosh(v);
    printf("The acosh(%.2f) = %.2lf in radians\n", v, output);

    //radians to degree convertion
    output = acosh(v)*180/PI;
    printf("The acosh(%.2f) = %.2lf in degrees\n", v, output);

    // paramter not in range
    v = 0.5;
    output = acosh(v);
    printf("The acosh(%.2f) = %.2lf", v, output);

    return 0;


The acosh(5.90) = 2.46 in radians
The acosh(5.90) = 141.00 in degrees
The acosh(0.50) = nan

Example 2: How acoshf() and acoshl() functions worked in C?

#include <stdio.h>
#include <math.h>
int main()
    float f, fcosx;
    long double l, lcosx;

    // type float
    f = 5.5054;
    fcosx = acoshf(f);

    //type long double
    l = 5.50540593;
    lcosx = acoshl(l);

    printf("acoshf(x) is equal to %f in radians\n", fcosx);
    printf("acoshl(x) is equal to %Lf in radians", lcosx);

    return 0;


acoshf(x) is equal to 2.390524 in radians
acoshl(x) is equal to 2.390525 in radians