function GetLength (x1, y1, x2, y2)
{
    var x = x1 - x2;
    var y = y1 - y2;
    var magnitude = (x * x) + (y * y);

    return Math.sqrt(magnitude);
}
Returns the length of the line.

@ignore
@private

@param {number} x1 - The x1 coordinate.
@param {number} y1 - The y1 coordinate.
@param {number} x2 - The x2 coordinate.
@param {number} y2 - The y2 coordinate.

@return {number} The length of the line.