radar gun beam width ???

Question

I need the math formula To figure the beam with of a police radar gun.
The specs in the owners manual says beam with is 12 degrees of arc.
What formula would I use to figure the beam width at different distances.

Answer 1

♦ draw a pic and see that 12° are 12° at any distance x, also see that r/x=tan(12°/2), where r is radius of the spot;

Answer 2

I won't do the work for you, but here's a hint - do a search on "trigonometry" - you are basically working with a triangle here.