Constructs an angle from the provided parameter
Constructs the angle of the given vector. X-axis is 0, counterclockwise.
Constructs an angle of a 2d vector (dx,dy)
Constructs the angle
Constructs the angle that is enclosed by the two vectors (between 0 and Math.PI)
Constructs the angle that is needed to rotate the first vector counterclockwise to reach the second vector (between 0 and 2.0*Math.PI)