#| BEGIN (Write your solution here) |#
(define (cont-frac n d k)
  (define (iter k res)
    (if (= k 0)
        res
        (iter (- k 1) (/ (n k) (+ (d k) res)))))
  (iter k 0))

(define (tan-cf x k)
  (cont-frac (lambda (i) (if (= i 1)
                             x
                             (- (* x x))))
             (lambda (i) (- (* i 2) 1))
             k))
#| END |#