Racket: fibonacci and sum

(define (fibo n)
  (cond
    ((= n 0) 1)
    ((= n 1) 1)
    (true (+ (fibo (- n 1)) (fibo (- n 2))))
    )
  )

(define (sumofint n)
  (cond
    ((= n 0) 0)
    (true (+ (sumofint (- n 1)) n))
    )
  )

(define (fibo n)
  (cond
    ((= n 0) 0)
    ((= n 1) 1)
    (true (+ (fibo (- n 1)) (fibo (- n 2))))
    )
  )

(fibo 0) wanna 0, describe in https://en.wikipedia.org/wiki/Fibonacci_number