Exercício 4 capítulo 3

--ep4
fatorial x  | (x==1) = 1
            | otherwise = x * fatorial (x-1)

e_x x n | (n==0) = 1
        | otherwise = ( (x**n) / fatorial n ) + (e_x x (n-1) )

delta' x n  | ((exp x) - (e_x x n)) < 0.001 = 0
            | otherwise = 1 + delta' x (n+1)

delta x = delta' x 0