October 29, 2018
Exercise 1.39: A continued fraction representation of the tangent function was published in 1770 by the German mathematician J.H. Lambert:
x is in radians. Define a procedure
(tan-cf x k) that computes an approximation to the tangent function based on Lambert’s formula.
k specifies the number of terms to compute, as in Exercise 1.37.
From what is already done, the solution is:
(define (cont-frac-iter n d k) (define (iter i result) (if (= 0 i) result (iter (sub1 i) (/ (n i) (+ result (d i)))))) (iter (sub1 k) (/ (n k) (d k)))) (define (tan-cf x k) (cont-frac-iter (lambda (i) (if (= i 1) x (* x x -1))) (lambda (i) (- (* 2.0 i) 1)) k)) ; check result (define x 1) (display (tan-cf x 8)) (newline) (display (tan x)) (newline)