# C# Math - Acosh() Function

The C# Acosh() function returns inverse hyperbolic cosine of a value. The inverse hyperbolic cosine of x is defined as:

In special cases it returns the following:

• If the argument is NaN, the method returns NaN.
• If the value of argument is less than 1, the method returns NaN.

### Syntax

```public static double Acosh (double x);
```

### Parameters

 `x` Specify the value.

### Return Value

Returns the inverse hyperbolic cosine of a value.

### Example:

In the example below, Acosh() function is used to find out the inverse hyperbolic cosine of a value.

```using System;

class MyProgram {
static void Main(string[] args) {
Console.WriteLine("Math.Acosh(0) = "
+ Math.Acosh(0));
Console.WriteLine("Math.Acosh(1) = "
+ Math.Acosh(1));
Console.WriteLine("Math.Acosh(2) = "
+ Math.Acosh(2));
Console.WriteLine("Math.Acosh(Double.NaN) = "
+ Math.Acosh(Double.NaN));
Console.WriteLine("Math.Acosh(Double.NegativeInfinity) = "
+ Math.Acosh(Double.NegativeInfinity));
Console.WriteLine("Math.Acosh(Double.PositiveInfinity) = "
+ Math.Acosh(Double.PositiveInfinity));
}
}
```

The output of the above code will be:

```Math.Acosh(0) = NaN
Math.Acosh(1) = 0
Math.Acosh(2) = 1.31695789692482
Math.Acosh(Double.NaN) = NaN
Math.Acosh(Double.NegativeInfinity) = NaN
Math.Acosh(Double.PositiveInfinity) = Infinity
```

❮ C# Math Methods

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