Math.atanh()

The Math.atanh() function returns the hyperbolic arctangent of a number, that is

$$\forall x \in \left( -1, 1 \right), \mathtt{\operatorname{Math.atanh}(x)} = \operatorname{arctanh}(x) = \text{ the unique } ; y ; \text{such that} ; \tanh(y) = x$$

x

A number.

The hyperbolic arctangent of the given number.

Because atanh() is a static method of Math, you always use it as Math.atanh(), rather than as a method of a Math object you created (Math is not a constructor).

Math.atanh(-2);  // NaN
Math.atanh(-1);  // -Infinity
Math.atanh(0);   // 0
Math.atanh(0.5); // 0.5493061443340548
Math.atanh(1);   // Infinity
Math.atanh(2);   // NaN

For values greater than 1 or less than -1, NaN is returned.

For $\left|x\right| < 1$, we have $\operatorname {artanh} (x) = \frac{1}{2}\ln \left( \frac{1 + x}{1 - x} \right)$ so this can be emulated by the following function:

Math.atanh = Math.atanh || function(x) {
  return Math.log((1+x)/(1-x)) / 2;
};

• A polyfill of Math.atanh is available in core-js
• Math.acosh()
• Math.asinh()
• Math.cosh()
• Math.sinh()
• Math.tanh()