(* sin approx *)
let sin (x : float):float =
    let nth (n: float) (x : float) : float = (* gives nth element for fiven x *)
        let rec fact (x:float) : float =
            if x = 0.0 then 1.0
            else x *. (fact(x -. 1.0)) in
                (-1.0)**(n +. 1.0) *. x**(2.0*.n -. 1.0) /. fact (2.0*.n -. 1.0) in
    let rec sin_tay (acc:float) (element:float) : float =
        let new_acc : float = acc +. nth element x  in
        if new_acc <> acc (*stop on precision error*)
            then sin_tay new_acc (element +. 1.0)
            else new_acc
        in
    sin_tay 0.0 1.0;; (*intitial value of acc = 0, starting from first element*)