title: If M is a turing machine, the question if L(M) = A Regular Language, Decidable?
body: <p>If M is a turing machine, we can construct a Context Sensitive Grammar G, and then check if the context sensitive grammar is context free, and finally context free grammar is regular or not in a way as described.<br>
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  If A Context sensitive grammar G is Context Free, if contains only nonterminals on the left, and if it is regular as well, it contains nonterminals at the end of production rules. </p>