f(x) = If[x ≥ 1, 1 / x]
a = Integral(f, 1, 10^(10))
b = Surface(t, (1 / t * cos(s)), (1 / t * sin(s)), t, 1, 20, s, 0, (2 * π))
g(x) = If[x ≥ 1, (1 / x * sqrt(1 + 1 / x^(4)))]