■ 🕑 11. some sample lisp code
   (define pi 3.14159265)
   (define (square x) (* x x))
   
   (define (volume-of-cone radius height)
   	(* pi (square radius) (/ height 3)))
   
   (define my-cone-volume (volume-of-cone 1 2))
   
   my-cone-volume
   => 2.09