[quote user="Barry Lothian"]The value provided as viewed in locals window/debug.print is measured clockwise from the x-axis.[/quote]
The number is negative. It's not really the inverse, just another way of presenting the result. Subtract from 2π to get the anti-clockwise value. Depending on the algorithms used, this kind of result can happen when an angle is greater than 180°. That's another reason to prefer working with matrices over angles, especially in 3D. Unfortunately most people can't interpret a rotation matrix: I blame the government.