If f:R→R be defined as follows: f(x)=1 x∈Q-1 x∉Q find (i) f(x)=(12), f(π) (ii) pre-image of 1 or -1

If $f : R \to R$ be defined as follows: $f (x) = \{\begin{cases} 1 x \in Q \\ - 1 x \notin Q \end{cases}$ find (i) $f (x) = (\frac{1}{2})$ , $f (π)$ (ii) pre-image of 1 or -1

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