연습문제 2.47

(define (make-frame origin edge1 edge2)
  (list origin edge1 edge2))

인 경우

(define (origin frame)
  (car frame))

(define (edge1 frame)
  (car (cdr frame)))

(define (edge2 frame)
  (car (cdr (cdr frame))))

이며

(define (make-frame origin edge1 edge2)
  (cons origin (cons edge1 edge2)))

인 경우

(define (origin frame)
  (car frame))

(define (edge1 frame)
  (car (cdr frame)))

(define (edge2 frame)
  (car (cdr (cdr frame))))