#| BEGIN (Write your solution here) |#
(define (square x) (* x x))

(define (cont-frac n d k)
  (define (iter i n d k)
    (if (= i k)
        (/ (n i) (d i))
        (/ (n i) (+ (d i) (iter (+ i 1) n d k)))))
  (iter 1 n d k))

(define (tan-cf x k)
  (define (iter i acc x k)
    (cond ((= i k)
           (/ (square x) acc))
          ((= i 1)
           (/ x (- acc (iter (+ i 1) (+ acc 2) x k))))
          (else
           (/ (square x) (- acc (iter (+ i 1) (+ acc 2) x k))))))
  (iter 1 1 x k))
#| END |#