Sine and cosine implementation in F# using the Taylor series?

SinCos.fsx

open System

let degToRad deg = deg * (Math.PI / 180.0)

// This is a very slow implementation of the sine function, and could be easily
// optimized in a lot of ways, but I wanted to know how to calculate sine, and
// this works.
// Taken from the accepted answer at:
// https://math.stackexchange.com/questions/501660/is-there-a-way-to-get-trig-functions-without-a-calculator
let sine angle places =
    [1 .. places] |> List.fold (fun counter value ->
        let pow = (((float value) * 2.0) + 1.0)
        let numerator = angle ** pow
        let denominator = [2.0 .. pow] |> List.fold ( * ) 1.0
        let result = numerator / denominator
        if value % 2 = 0
        then counter + result
        else counter - result
    ) angle

sine (degToRad 27.0) 4


// Just for kicks, here's a definition for cosine too. As above, this is slow,
// use Math.Sin and Math.Cos for real work, but it's interesting to write a
// working implementation.
let cosine angle places =
    [1 .. places] |> List.fold (fun counter value ->
        let pow = ((float value) * 2.0)
        let numerator = angle ** pow
        let denominator = [2.0 .. pow] |> List.fold ( * ) 1.0
        let result = numerator / denominator
        if value % 2 = 0
        then counter + result
        else counter - result
    ) 1.0

cosine (degToRad 27.0) 4