;; constant
(define PI 3.142)

;; square : number -> number
(define (square x) (* x x))

;; area-circle : number -> number
(define (area-circle radius)
  (* PI (square radius)))

;; volume-cylinder : number number -> number
;; formula = pi r^2 h
(define (volume-cylinder radius height)
  (* (area-circle radius) height))