(define(symtree? tree)
  (define(symT tree tree2)
  ((cond((and(emptytree? tree)(emptytree? tree2)) #t )
        ((and(leaf? tree)(leaf? tree2)) #t)
        ((and(emptytree? tree)(not(emptytree? tree2))) #f )
        ((and(emptytree? tree2)(not(emptytree? tree2))) #f)
        (else (and(symT (leftree tree)(righttree tree2))
                  (symT (rightree tree)(lefttree tree2)))
    )
  (symT tree tree)
  )