Beginner Question Thread! 2023 Edition

[Plurf]

begginer in mathematics question ^^

@Plurf

a little mathematic riddle for you nerds :

One cells has a radius of 21mm
The minimum width of the enclosure is 225mm
I want to feet 12 cells parallel to the deck

How do I calculate the angle between each cells using only algeabrae and not geometrie ?

Here is what I did, geometrically, it’s good enough to work with but I’d have loved to find a more mathematical approach :

225 - 21 (that is half the radius on both side) = 204
204 / 11 = 18.5454 Which is the string at contact point between each radius
and then it’s geometrically immediate to feet them, and I can measure the angle