Lemma 64.6.2. An object E of D(\mathcal{A}) is contained in D^+(\mathcal{A}) if and only if H^ i(E) =0 for all i \ll 0. Similar statements hold for D^- and D^ b.
Proof. Hint: use truncation functors. See Derived Categories, Lemma 13.11.5. \square
Lemma 64.6.2. An object E of D(\mathcal{A}) is contained in D^+(\mathcal{A}) if and only if H^ i(E) =0 for all i \ll 0. Similar statements hold for D^- and D^ b.
Proof. Hint: use truncation functors. See Derived Categories, Lemma 13.11.5. \square
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