angle(0,0,Gamepad.Axis(0, 0), Gamepad.Axis(0, 1)) is the angle of the left thumbstick
so you can set and invisible sprite object to that angle every tick
every tick - set sprite angle to angle(0,0,Gamepad.Axis(0, 0), Gamepad.Axis(0, 1))
then if you check the angle of that sprite eg: it will give you a value between 0 and 360 degrees
you can then divide that angle by 12 or however many slices as you need
The easiest way for a GTA type circle weapon picking thing would be to create a invisible rectangle with a pivot point at one end. Place it in the center of your selection ring.
every tick set rectangle angle to angle(0,0,Gamepad.Axis(0, 0), Gamepad.Axis(0, 1))
on button press if rectangle is overlapping circle piece, then select that weapon.
use it as a cursor of sorts to pick which slice is selected.
this way you dont have to deal with any math either.. (i'm sure there's a fancier mathematical way to do this)