It was proved in the 1990s that R exp is model complete, which combined with Khovanskiĭ's theorem on Pfaffian functions proves that R exp is also o-minimal.
It was proved in the 1990s that R exp is model complete, a result known as Wilkie's theorem. This result, when combined with Khovanskiĭ's theorem on pfaffian functions, proves that R exp is also o-minimal.