EN
Given an o-minimal expansion ℳ of a real closed field R which is not polynomially bounded. Let $𝓟^{∞}$ denote the definable indefinitely Peano differentiable functions. If we further assume that ℳ admits $𝓟^{∞}$ cell decomposition, each definable closed subset A of Rⁿ is the zero-set of a $𝓟^{∞}$ function f:Rⁿ → R. This implies $𝓟^{∞}$ approximation of definable continuous functions and gluing of $𝓟^{∞}$ functions defined on closed definable sets.