26-221512.scm

(define (three a b c)
  (cond ((and (< a b) (< a c)) (+ (* b b) (* c c)))
        ((and (< b a) (< b c)) (+ (* a a) (* c c)))
        (else (+ (* a a) (* b b)))))
(print (three 3 4 5))
(print (three 5 4 3))
(print (three 4 3 5))

26-223719.scm

(define (sqrt-iter guess x)
  (if (good-enough? guess x)
      guess
      (sqrt-iter (improve guess x)
                 x)))

(define (improve guess x)
  (average guess (/ x guess)))

(define (average x y)
  (/ (+ x y) 2))

(define (good-enough? guess x)
  (< (abs (- (square guess) x)) 0.001))

(define (sqrt x)
  (sqrt-iter 1.0 x))

;;

(print (sqrt 9))

(print (sqrt (+ 100 37)))

(print (sqrt (+ (sqrt 2) (sqrt 3))))

(print (square (sqrt 1000)))

(print (sqrt 0.000002))

(print (sqrt 200000000000000000000))

26-223907.scm

(define (new-if predicate then-clause else-clause)
  (cond (predicate then-clause)
        (else else-clause)))

(define (sqrt-iter guess x)
  (new-if (good-enough? guess x)
          guess
          (sqrt-iter (improve guess x)
                     x)))

(define (improve guess x)
  (average guess (/ x guess)))

(define (average x y)
  (/ (+ x y) 2))

(define (good-enough? guess x)
  (< (abs (- (square guess) x)) 0.001))

(define (sqrt x)
  (sqrt-iter 1.0 x))

(print (sqrt 9))

(print (sqrt (+ 100 37)))

(print (sqrt (+ (sqrt 2) (sqrt 3))))

(print (square (sqrt 1000)))

p-1-1.scm

#?=(+ 5 3 4)
#?=(- 9 1)
#?=(/ 6 2)
#?=(+ (* 2 4) (- 4 6))
(define a 3)
(define b (+ a 1))
#?=(+ a b (* a b))
#?=(= a b)
#?=(if (and (> b a) (< b (* a b)))
       b
       a)
#?=(cond ((= a 4) 6)
         ((= b 4) (+ 6 7 a))
         (else 25))
#?=(+ 2 (if (> b a) b a))
#?=(* (cond ((> a b) a)
            ((< a b) b)
            (else -1))
      (+ a 1))