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;;;; Under Creative Commons Attribution-ShareAlike 4.0
;;;; International. See
;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
(define-module (net ricketyspace sicp one thirtynine)
#:use-module (net ricketyspace sicp one thirtyseven)
#:export (tan-cf))
(define (tan-cf x k)
(define (n i) (if (= 1 i) x (* -1 (expt x 2.0))))
(define (d i) (1- (* 2.0 i)))
(cont-frac-rec n d k))
;;; GNU Guile REPL
;;;
;;; scheme@(guile-user)> ,use (net ricketyspace sicp one thirtynine)
;;; scheme@(guile-user)> (tan-cf 45 1000)
;;; $39 = 1.6197751905438595
;;; scheme@(guile-user)> (tan-cf 90 1000)
;;; $40 = -1.9952004122082423
;;; scheme@(guile-user)> (tan-cf 135 1000)
;;; $41 = -0.08871575677005962
;;; scheme@(guile-user)> (tan-cf 180 1000)
;;; $42 = 1.3386902103511542
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