# Math.Atanh(Double) Method

## Definition

Returns the angle whose hyperbolic tangent is the specified number.

```
public:
static double Atanh(double d);
```

`public static double Atanh (double d);`

`static member Atanh : double -> double`

`Public Shared Function Atanh (d As Double) As Double`

#### Parameters

- d
- Double

A number representing a hyperbolic tangent, where `d`

must be greater than or equal to -1, but less than or equal to 1.

#### Returns

An angle, θ, measured in radians, such that -∞ < θ < -1, or 1 < θ < ∞.

-or-

NaN if `d`

< -1 or `d`

> 1 or `d`

equals NaN.

## Remarks

Multiply the return value by 180/Math.PI to convert from radians to degrees.

This method calls into the underlying C runtime, and the exact result or valid input range may differ between different operating systems or architectures.