CS173: Discrete Math We say that f(x) is 𝛳(g(x)) if f(x) is O(g(x)) and f(x) is 𝛺(g(x)) When f(x) is 𝛳(g(x)) , we say f is big-Theta of g(x), and we also say f(x) is of order g(x) * Big Theta-notation When f(x) is 𝛳(g(x)), g(x) is 𝛳(f(x)) f(x) is 𝛳(g(x)) if and only if f(x) is O(g(x)) and g(x) is O(f(x)) * Example Let f(n)=1+2+…+n