Goat problem

Monte Carlo Goat.fs

let pi = System.Math.PI
let sqrt x = System.Math.Sqrt x
let inline squared x = x * x
let radiusA = 1.0
let radiusB = 1.158728 //should be "1.158728"
let area = pi*(radiusA**2.0)

let randr min max = System.Random.Shared.NextDouble() * (max - min) + min
let rand () = randr -1.0 1.0

let inside origo coordinate r =
    let (ox, oy) = origo
    let (x, y) = coordinate
    ((x-ox)**2.0) + ((y-oy)**2.0) |> sqrt < r

let findRatio length size =
    let mutable insideACount = 0
    let mutable insideAAndBCount = 0

    for _ in 0..size-1 do
        let x = rand()
        let y = rand()

        if inside (0.0, 0.0) (x, y) radiusA then
            insideACount <- insideACount + 1

            if inside (radiusA, 0.0) (x, y) length then
                insideAAndBCount <- insideAAndBCount + 1

    //let ratio = (insideACount |> float) / (size |> float)
    //let monteArea = ratio * (radiusA**2)*4.0
    (insideAAndBCount |> float) / (insideACount |> float)

let start = 0.0
let stop = 2.0

let mutable size = 1000
let mutable increment = 0.1
let mutable current = start

while true do
    printfn "Trying %f with %i iterations" current size
    let ratio = findRatio current size
    printfn "Got ratio %f" ratio
    if ratio > 0.5 then
        current <- current - increment
        increment <- increment * 0.95
        size <- ((size |> float) * 1.1) |> int
    else
        current <- current + increment