NormalY = function (line)
{
    return Math.sin(Angle(line) - MATH_CONST.TAU);
}
The Y value of the normal of the given line.
The normal of a line is a vector that points perpendicular from it.

@function Phaser.Geom.Line.NormalY
@since 3.0.0

@param {Phaser.Geom.Line} line - The line to calculate the normal of.

@return {number} The Y value of the normal of the Line.