Ex 2.46

(define (make-vect x y) (list x y))

(define (xcor-vect v) (car v))

(define (ycor-vect v) (cadr v))

(define (add-vect a b)
  (make-vect (+ (xcor-vect a) (xcor-vect b)) (+ (ycor-vect a) (ycor-vect b))))

(define (sub-vect a b)
  (make-vect (- (xcor-vect a) (xcor-vect b)) (- (ycor-vect a) (ycor-vect b))))

(define (scale-vect s v)
  (make-vect (* s (xcor-vect v)) (* s (ycor-vect v))))