I have these two semigroups(ℝ≥0, +)and(ℝ≥1, *)where * is multiplication.

How can I show that these are isomorphic?

I know from wikipedia that:

"Two semigroups S and T are said to be isomorphic if there is a bijection f : S ↔ T with the property that, for any elements a, b in S, f(ab) = f(a)f(b). Isomorphic semigroups have the same structure."

But I have no idea on how to go about proving this. Any help would be highly appreciated.