function getWavelength( T, h ) {
    const g = 9.81;
    const PI = Math.PI;
    var shallow = T*Math.sqrt(g*h);
    if ( h/shallow < 0.05) {
        return shallow;
    }

    var deep = T*T*g/2*PI;
    if ( h/deep > 0.5) {
        return deep;
    }

    var len = deep;
    var temp = len;
    var diff = len;
    while ( Math.abs(diff) > 0.0001) {
        temp = T*T*tanh(2*PI*h/len)*g/(2*PI);
        diff = len - temp;
        len = temp;
    }
    return len;
}

function checkDepth( h, lambda ) {
    if ( h/lambda > 0.5) {
        return 'd';
    }
    if ( h/lambda < 0.05 ) {
        return 's';
    }
    return 'f';
}

function waveProfile( zeta, omega, k, t, x ) {
    return zeta*Math.sin(omega*t - k*x);
}

function dynamicPressure( type, h, zeta, omega, k, t, x, z) {
    const g = 9.81;
    const rho = 1000;

    var Pd = rho*g*zeta*Math.sin(omega*t - k*x);

    if (type == 'd') {
        Pd = Pd*Math.exp(k*z);
    } else if (type == 'f') {
        Pd = Pd*cosh(k*(z + h))/cosh(k*h);
    }

    return Pd;
}

function calculateRightingArm(GM, angle) {
    return GM*Math.sin(angle);
}