Lyapunov stability and Lasalle's Theorem

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If a given function V is radially unbounded, does it also imply that it is positive definite? I am trying to solve a stability problem (prove GAS) with and without Lasalle's theorem. It is easy enough to solve using Lasalle's theorem as I can prove the function is radially unbounded but do not know how to see if V (Lyapunov function) is positive definite.