The AngleInRad property allows the vector interface to be used as a 2D angle (in radians). The Axis Index controls which 2 axis of the vector are used. Use the AngleInRad property to get the angle represented by the Axis pair values in the X, Y , and/or Z properties. When the AngleInRad property is set, it modifies the axis pair so that it equals the angle given. However, it should attempt to preserve the Magnitude of the vector.
The AngleInRad property gets and sets the angle of the vector in radians. Use the Angle property to get and set the angle of the vector in degrees.