Returns the hyperbolic sine of a double. - Java java.lang

Java examples for java.lang:Math Trigonometric Function

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Description

Returns the hyperbolic sine of a double.

Demo Code

/*//www.  j  a  v a2 s .  c om
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//package com.java2s;

public class Main {
    private static final double SINH_COEF[] = { 0.1730421940471796,
            0.08759422192276048, 0.00107947777456713, 0.00000637484926075,
            0.00000002202366404, 0.00000000004987940, 0.00000000000007973,
            0.00000000000000009 };

    /**
     * Returns the hyperbolic sine of a double.
     * 
     * @param x
     *            A double value.
     * @return The arc hyperbolic sine of x. If x is NaN or less than one, the
     *         result is NaN.
     */
    static public double sinh(double x) {
        double ans;
        double y = Math.abs(x);

        if (Double.isNaN(x)) {
            ans = Double.NaN;
        } else if (Double.isInfinite(y)) {
            return x;
        } else if (y < 2.58096e-08) {
            // 2.58096e-08 = Math.sqrt(6.0*EPSILON_SMALL)
            ans = x;
        } else if (y <= 1.0) {
            ans = x * (1.0 + csevl(2.0 * x * x - 1.0, SINH_COEF));
        } else {
            y = Math.exp(y);
            if (y >= 94906265.62) {
                // 94906265.62 = 1.0/Math.sqrt(EPSILON_SMALL)
                ans = sign(0.5 * y, x);
            } else {
                ans = sign(0.5 * (y - 1.0 / y), x);
            }
        }
        return ans;
    }

    static double csevl(double x, double coef[]) {
        double b0, b1, b2, twox;
        int i;
        b1 = 0.0;
        b0 = 0.0;
        b2 = 0.0;
        twox = 2.0 * x;
        for (i = coef.length - 1; i >= 0; i--) {
            b2 = b1;
            b1 = b0;
            b0 = twox * b1 - b2 + coef[i];
        }
        return 0.5 * (b0 - b2);
    }

    static private double sign(double x, double y) {
        double abs_x = ((x < 0) ? -x : x);
        return (y < 0.0) ? -abs_x : abs_x;
    }
}

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