nd4j-common/src/main/java/org/nd4j/linalg/util/BigDecimalMath.java
static public BigDecimal tanh(final BigDecimal x) {
        if (x.compareTo(BigDecimal.ZERO) < 0) {
            return tanh(x.negate()).negate();
        } else if (x.compareTo(BigDecimal.ZERO) == 0) {
            return BigDecimal.ZERO;
        } else {
            BigDecimal xhighpr = scalePrec(x, 2);
            /* tanh(x) = (1-e^(-2x))/(1+e^(-2x)) .
             */
            BigDecimal exp2x = exp(xhighpr.multiply(new BigDecimal(-2)));
            /* The error in tanh x is err(x)/cosh^2(x).
             */


            double eps = 0.5 * x.ulp().doubleValue() / Math.pow(Math.cosh(x.doubleValue()), 2.0);
            MathContext mc = new MathContext(err2prec(Math.tanh(x.doubleValue()), eps));


            return BigDecimal.ONE.subtract(exp2x).divide(BigDecimal.ONE.add(exp2x), mc);


        }
    }
static public BigDecimal tanh(final BigDecimal x) {
        if (x.compareTo(BigDecimal.ZERO) < 0) {
            return tanh(x.negate()).negate();
        } else if (x.compareTo(BigDecimal.ZERO) == 0) {
            return BigDecimal.ZERO;
        } else {
            BigDecimal xhighpr = scalePrec(x, 2);
            /* tanh(x) = (1-e^(-2x))/(1+e^(-2x)) .
             */
            BigDecimal exp2x = exp(xhighpr.multiply(new BigDecimal(-2)));
            /* The error in tanh x is err(x)/cosh^2(x).
             */


            double eps = 0.5 * x.ulp().doubleValue() / Math.pow(Math.cosh(x.doubleValue()), 2.0);
            MathContext mc = new MathContext(err2prec(Math.tanh(x.doubleValue()), eps));


            return BigDecimal.ONE.subtract(exp2x).divide(BigDecimal.ONE.add(exp2x), mc);


        }
    }
static public BigDecimal tanh ( final BigDecimal x ) { if ( x . compareTo ( BigDecimal . ZERO ) < 0 ) { return tanh ( x . negate ( ) ) . negate ( ) ; } else if ( x . compareTo ( BigDecimal . ZERO ) == 0 ) { return BigDecimal . ZERO ; } else { BigDecimal xhighpr = scalePrec ( x , 2 ) ; /* tanh(x) = (1-e^(-2x))/(1+e^(-2x)) .
             */ BigDecimal exp2x = exp ( xhighpr . multiply ( new BigDecimal ( - 2 ) ) ) ; /* The error in tanh x is err(x)/cosh^2(x).
             */ double eps = 0.5 * x . ulp ( ) . doubleValue ( ) / Math . pow ( Math . cosh ( x . doubleValue ( ) ) , 2.0 ) ; MathContext mc = new MathContext ( err2prec ( Math . tanh ( x . doubleValue ( ) ) , eps ) ) ; return BigDecimal . ONE . subtract ( exp2x ) . divide ( BigDecimal . ONE . add ( exp2x ) , mc ) ; } }
The hyperbolic tangent.

@param x The argument.
@return The tanh(x) = sinh(x)/cosh(x).
The hyperbolic tangent .