Formatting double to latitude/longitude human readable format

Question

If the formula for converting latitude or longitude to double is

((Degree) + (Minute) / 60 + (Second) / 3600) * ((South || West) ? -1 : 1)

then what's the formula for parsing degrees, minutes, seconds from a double?

It'd make sense to have two separate methods for parsing latitude and longitude, but I'm not sure how to parse the degrees, minutes, seconds from the double.

ParseLatitude(double value)
{
    //value is South if negative, else is North.
}

ParseLongitude(double value)
{
    //value is West if negative, else is East.
}

Example coordinates:

latitude: 43.81234123

longitude: -119.8374747

The final code to convert back and forth, thanks again to Peter and James for the answer. I had to convert value to Decimal because this is being used in Silverlight and Math.Truncate(double) is not available):

public class Coordinate
{
    public double Degrees { get; set; }
    public double Minutes { get; set; }
    public double Seconds { get; set; }
    public CoordinatesPosition Position { get; set; }

    public Coordinate() { }
    public Coordinate(double value, CoordinatesPosition position)
    {
        //sanity
        if (value < 0 && position == CoordinatesPosition.N)
            position = CoordinatesPosition.S;
        //sanity
        if (value < 0 && position == CoordinatesPosition.E)
            position = CoordinatesPosition.W;
        //sanity
        if (value > 0 && position == CoordinatesPosition.S)
            position = CoordinatesPosition.N;
        //sanity
        if (value > 0 && position == CoordinatesPosition.W)
            position = CoordinatesPosition.E;

        var decimalValue = Convert.ToDecimal(value);

        decimalValue = Math.Abs(decimalValue);

        var degrees = Decimal.Truncate(decimalValue);
        decimalValue = (decimalValue - degrees) * 60;

        var minutes = Decimal.Truncate(decimalValue);
        var seconds = (decimalValue - minutes) * 60;

        Degrees = Convert.ToDouble(degrees);
        Minutes = Convert.ToDouble(minutes);
        Seconds = Convert.ToDouble(seconds);
        Position = position;
    }
    public Coordinate(double degrees, double minutes, double seconds, CoordinatesPosition position)
    {
        Degrees = degrees;
        Minutes = minutes;
        Seconds = seconds;
        Position = position;
    }
    public double ToDouble()
    {
        var result = (Degrees) + (Minutes) / 60 + (Seconds) / 3600;
        return Position == CoordinatesPosition.W || Position == CoordinatesPosition.S ? -result : result;
    }
    public override string ToString()
    {
        return Degrees + "º " + Minutes + "' " + Seconds + "'' " + Position;
    }
}

public enum CoordinatesPosition
{
    N, E, S, W
}

Unit Test (nUnit)

[TestFixture]
public class CoordinateTests
{
    [Test]
    public void ShouldConvertDoubleToCoordinateAndBackToDouble()
    {
        const double baseLatitude = 43.81234123;
        const double baseLongitude = -119.8374747;

        var latCoordN = new Coordinate(baseLatitude, CoordinatesPosition.N);
        var latCoordS = new Coordinate(baseLatitude, CoordinatesPosition.S);
        var lonCoordE = new Coordinate(baseLongitude, CoordinatesPosition.E);
        var lonCoordW = new Coordinate(baseLongitude, CoordinatesPosition.W);

        var convertedLatitudeS = latCoordS.ToDouble();
        var convertedLatitudeN = latCoordN.ToDouble();
        var convertedLongitudeW = lonCoordW.ToDouble();
        var convertedLongitudeE = lonCoordE.ToDouble();

        Assert.AreEqual(convertedLatitudeS, convertedLatitudeN);
        Assert.AreEqual(baseLatitude, convertedLatitudeN);
        Assert.AreEqual(convertedLongitudeE, convertedLongitudeW);
        Assert.AreEqual(baseLongitude, convertedLongitudeE);
    }
}