# Acosh

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# Syntax

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

# Description

Returns the nonnegative arc hyperbolic cosine of x, expressed in radians.

The arc hyperbolic cosine is the inverse operation of the hyperbolic cosine.

# Parameters

- x
- Value whose arc hyperbolic cosine is computed.
- If the argument is less than 1, a domain error occurs.

# Return Value

Nonnegative arc hyperbolic cosine of x, in the interval [0,+INFINITY] radians.

*Note that the negative of this value is also a valid arc hyperbolic cosine of x One radian is equivalent to 180/PI degrees.*

If a domain error occurs:

- And math_errhandling has MATH_ERRNO set: the global variable errno is set to EDOM.
- And math_errhandling has MATH_ERREXCEPT set: FE_INVALID is raised.