(defn cont-frac [N D k]
  (defn iter [prev i]
    (if (>= i k)
      prev
      (cond
        (= i 1) (iter (/ (N (- k i)) (D (- k i))) (+ i 1))
        (iter (/ (N (- k i)) (- (D (- k i)) prev)) (+ i 1)))))
  (iter 0 1))

(defn tan-cf [x k]
  (defn odd [i] (- (* i 2) 1))
  (defn N [i]
    (cond
      (= i 1) x
      (* x x)))
  (cont-frac N odd k))

(print (tan-cf 1 100))